In the ongoing effort to try to keep the playing field as equal as possible in professional sports, sometimes rule books have to be amended, or -- at the very least -- new rules have had to be enacted that puts a limit to the advantage one player might have over another. This is especially true if players try to exploit the specific language of the rules, where their defense is typically along the lines of "Well, there isn't a rule saying that I can't do this tactic for my advantage."

This list is going to highlight fifteen players who brought about specific rule changes in their sport. Not all of them have to do with specific unfair advantages though, as a lot of them have to do with player safety, eligibility, or simply no longer being allowed to exploit situations that arise in any given game. For example, no goaltender in hockey wants to have a skater do the "I'm not touching you" routine that every sibling had to endure while growing up in the same house. Everyone thinks that's annoying, but at the same time it technically didn't break any rules...

So let's take a look at fifteen times where players caused alterations to their rule books!

15 15. Sean Avery

This is a very interesting situation and it's the one we alluded to in the introduction to this piece. Sean Avery was a known pest for the New York Rangers in the 2008 playoffs against the New Jersey Devils, and he made it a point to distract snf annoy one person: Martin Brodeur. Instead of lining up in front of the net with your backed turned creating a conventional screen, Sean Avery decided to wave his stick around Brodeur's face in a small game of "I'm not touching you" just to try to annoy him and yell for his mom to make Avery stop. Brodeur tried shoving him away and smacking him with his glove, but Avery would go right back to being the nuisance that he was insisting on being. It technically wasn't against any rules, but the NHL quickly stepped in and amended the rule book to show that any act of that nature would result in a two minute unsportsmanlike penalty.

14 14. Buster Posey

Collisions at home plate have been a part of baseball since its inception, but after enough players get injured, it's probably not a good idea to keep it around just for the sake of history. The San Francisco Giants know this all too well after they lost their premier catcher Buster Posey for the remainder of the 2011 season and the league responded by modifying the rules about collisions at the plate. Catchers can no longer block a runner's path to the plate before they possess the ball, and runners can no longer shoulder tackle a catcher in an attempt to try to dislodge the ball from his glove/hand. Runners don't necessarily have to slide into home, but old-school collisions will no longer be tolerated. Interestingly enough, the rule wasn't implemented until a couple of years after the incident with Buster Posey, but he will forever be associated with the rule taking effect due to the major injury he sustained.

13 13. Chase Utley

Perhaps the most recent player to have a rule changed, Chase Utley was also attempting to do what had been done in baseball for over a hundred years. While sliding into second base in order to prevent a routine double play, Utley clearly went out of his way to make heavy contact with Ruben Tejada's legs to try to break it up. What happened was Utley sliding way too late and slamming his head directly into Tejada's leg, breaking it in the process. Major League Baseball was quick to make changes to the rules by stating that runners must make a clear attempt to slide into the base, must slide before the base, must remain on the base after sliding, and they cannot deviate their path away from the base in order to make contact with the infielder. However, they are still allowed to initiate contact to try to break up potential double plays if they abide by all of the aforementioned aspects to the new rule.

12 12. Calvin Johnson

The NFL has had its fair share of questionable rule interpretations throughout the years, but you'd like to think that something so fundamental like defining what a proper catch is wouldn't be so difficult. In a game against the Chicago Bears, Detroit Lions receiver Calvin Johnson did all of the following in one motion: jumped up and clearly caught a would-be touchdown pass in the end zone, landed with both feet in bounds, took a couple of steps backward, and slid on the ground with his left hip before sliding out of the back of the end zone. Possession was clearly established and Johnson did everything he could to maintain his grip on the football, but the officials that day saw otherwise. They concluded that despite all of the evidence suggesting that Johnson caught the ball cleanly that he "lost possession" after he let go of the ball on the ground to go celebrate the touchdown. Similar plays are now often referred to as the "Calvin Johnson Rule," which states that a player must maintain possession throughout the entire "process," despite the fact that, you know, the ground cannot cause a fumble. To this day it remains a problem in the NFL...

11 11. Ilya Kovalchuk

Not so much a rule change that has anything to do with how the sport is played but more about how salaries count against the annual salary cap. In February of 2010, the New Jersey Devils signed Ilya Kovalchuk to a MASSIVE 17 year/$102 million deal that would have kept him in Jersey until he was well into his 40s. The NHL rejected the contract the very next day because it was clear that New Jersey had found a loophole in the salary structure for players. What they had tried to do was cheat the system by paying Kovalchuk a large portion of his contract in his early years (which is called "front-loading") and then pay him next to nothing in his later years when it was highly likely that he would have probably retired by then. This gave them a huge advantage because he would have been paid over $10 million for five seasons, but the cap hit against the team would have only been $6 million for each year. This was back when there wasn't a rule about having the annual average value (or AAV) against the cap be consistent with the formula "dollar amount divided by contract length," for which Kovalchuk is essentially responsible.

10 10. Stan Mikita

For all of you young hockey fans out there, hockey stick blades used to be completely flat, that is until -- and this is according to the legend himself -- Stan Mikita started to experiment one day with a stick that had cracked during practice. Mikita fondly tells the story like this: he got his stick blade caught in the doorway between the bench and the hallway to the locker room and someone came up and pushed him from behind, cracking but not entirely breaking the blade. Angrily, he fired a puck toward the boards and noticed how much more velocity and upper movement his shot had (since he was now able to lift the puck far greater than before), so he got the idea to try to recreate the effect by essentially "cooking" a wooden stick so that the blade would bend in the manner that he wanted. He started using his new "banana blade" during games, but the NHL had to quickly intervene when they noticed just how bent the blade of his stick really was. Mikita claims to have bent his blades over three inches, but a new rule was put into place to have them curve for a maximum of 3/4 of an inch.

9 9. Deion Sanders

Here's a quick fact about Deion Sanders: he very well might be the only football player to have two different rules changed; one in college and one in the NFL. The first is an on-going problem and one that student-athletes are subjected to on a daily basis: attending class. Deion was obviously going to become a professional athlete, but he had that pesky problem of having to actually take college courses in order to stay eligible. Well, he didn't. While at Florida State it was revealed that after he played in the 1989 Sugar Bowl, that he hadn't actually gone to school at all that semester, which apparently is a big no-no. The NCAA then started to heavily enforce their eligibility criteria.

The second rule had to do with the NFL and large signing bonuses. In 1995, Dallas Cowboys owner Jerry Jones back-loaded Sanders' contract so that they didn't have to pay him very much for the first three years of the contract and also gave him a $12.99 million bonus (actively trying to avoid a huge cap hit), forcing the NFL to make a rule stating that portions of large signing bonuses would now be incorporated into the salary cap each year in order to prevent teams from finding loopholes in the system and exploiting them for their benefit.

8 8. Trent Tucker

Here's a situation that should have been an absolute no-brainer but turned out to be awfully controversial when it happened. The Detroit Pistons and Chicago Bulls were tied at 106 with 00:00.1 seconds left on the game clock and Detroit was attempting to in-bound the ball. The obvious play with such little time remaining was to in-bound it directly toward the net to Patrick Ewing for a very quick alley-oop dunk, but that play was easily sniffed out by the Bulls. Trent Tucker then runs to the three point line and secures the in-bound pass, takes a quick shot and lands the game-winning shot. Now, you're probably saying to yourself that nobody can catch and release a shot in a tenth of a second, and you're right. The officials operating the clocks that night deduced that everything was working properly when they started their timers even though replay clearly showed that the clocks didn't start until well after Tucker had already released the ball, giving the Pistons a 109-106 victory. The "Trent Tucker Rule" then went into effect, stating that if the game clock shows anything less than 00:00.3 remaining, no shot will be counted as there is clearly not enough time to catch and release a basketball.

7 7. Roy Williams

It's doubtful that anyone else will ever be as closely associated with the infamous "horse-collar tackle" technique than the Dallas Cowboys' Roy Williams. For those unaware, a horse-collar tackle is when you grab the back of someone's jersey around the collar area and quickly yank down, slamming the backs of their heads into the ground without any real defense. The tackle was so effective and violent that Willaims injured three players in the same season (2004), which forced the NFL to step in and stop the madness that same year. Since he was practically one of the only ones to use this technique on a regular basis, his name became synonymous with the phrase and it was so controversial that Terrell Owens and Patrick Crayton spoke out about how they were not thrilled that he continued to use the maneuver well after it had already been banned.

6 6. Rob Ray

Have you ever wondered why your favorite knock-off NHL sweaters come fully-equipped with a "fight strap?" Rob Ray was the person who was responsible for that becoming a mandatory league-wide rule because he was notorious for engaging in fights, but it was his approach to them where the rule takes effect. He loved to take off his own sweater and also his shoulder and elbow pads so he could be more effective in his boxing abilities without being compromised by the bulky padding any longer, which led to the NHL deciding that all sweaters much be attached to your pants via the "fight strap," and anyone caught not doing so is subject to ejection from the game. The strap also serves a dual purpose: it was a very common practice to try to pull your opponent's jersey over their head so that they couldn't see your incoming punches, so that issue was also resolved.

5 5. Dwyane Wade

Officials who have to make judgment calls in real time for every game of basketball have to have the hardest jobs in all of sports. Nearly every play could be called as either an offensive or defensive foul, but no player has exploited this as much as Dwyane Wade, who routinely used to initiate contact with a defender's arms in the attempt to draw more fouls and subsequent free throw attempts. What he would do was catch his dribble and then make an attempt at throwing his arms into the defender, get the whistle for the foul, and then make another attempt to put up a shot so that it would technically be considered a shooting foul, regardless if the defending team was over the penalty limit or not. He used to do this with regularity, which the league wanted to put and end to after fans complained that the game was slowing down considerably.

4 4. Ricky Williams

Remember the Roy Williams entry and how you're not allowed to yank someone down by the collar of their jersey because of him? Apparently the NFL doesn't seem to care if you want to tackle someone by the hair, if it extends out beyond their helmets. Pretty contradictory, right? According to the rule, your hair is considered as an extension of your jersey if it makes contact with it by protruding out of the back of the helmet. But wait, if that's true, then why is a horse collar tackle not acceptable? If they're worried about player safety, you'd think that both tackles would be banned, but in the crazy minds of the NFL one is perfectly acceptable and the other is a worthy of a penalty. Ricky Williams is the player that has the honor of having this "hair rule" be associated with his lengthy dread locks, but several other athletes have had famously long locks, including Clay Matthews and Troy Polamalu, but they're defenders and are less likely to be taken down by their scalps.

3 3. Wayne Gretzky

Typically when one or more players exhibit a keen understanding of a rule and use it to their advantage over another team, discussions of outlawing said rule, or at least modifying it in part, start to take place. Perhaps one of the greatest examples of this was when Wayne Gretzky essentially had a rule changed in the NHL that prohibited coincidental minor penalties from going to 4 on 4 or 3 on 3 hockey for two minutes. The Edmonton Oilers were a powerhouse team throughout the 1980s and they developed a tactic of intentionally drawing offsetting penalties in order to give Wayne Gretzky, Mark Messier, and Jari Kurri more room around the ice in order to score more goals while two players were in the penalty box. They used this strategy so much that the league took notice and decided to put and end to their clever ruse. Gretzky held a press conference speaking out against the rule, but it would be seven years before they finally went back to having 4 on 4 coincidental minor penalties.

2 2. Tom Brady

For as much flack as football fans like to give Tom Brady, there's little doubt that he has been one of the greatest quarterbacks the game has ever seen. He's so important, in fact, that when he went out for an entire year in the very first week of the 2008 season with a blown ACL and MCL the league quickly enacted "The Tom Brady Rule," unofficially titled, of course. The rule states that defensive players can no longer make a desperation lunge at a quarterback's legs to try to tackle him to the ground. Brady was in the process of throwing a pass to Randy Moss when Bernard Pollard took out Brady's plant leg, which caused a serious injury to one of the NFL's most prized possessions. Not wanting to see similar things happen to their most important players, hits of this nature are now subject to harsh penalties and can even result in fines or suspensions.

1 1. Wilt Chamberlain

Wilt Chamberlain was so dominant in his era that he practically changed the sport single-handedly. So it doesn't surprise us in the least that at least a few things had to be changed about professional basketball in order to have a little more parity throughout the league. Chamberlain was responsible for the following rule changes during his career: the NBA widened the area in the paint from 11 feet to 15 feet to make it a little more difficult for him to score with ease, they instituted the offensive goaltending rule which disallowed offensive players from interfering with a ball directly over the rim, and they outlawed passes from out-of-bounds to be thrown directly over the hoop and immediately slammed home by an offensive player. But perhaps the funniest rule that the NBA enacted was the outlawing of intentionally fouling him whether or not he even had the ball, just for the sole purpose of forcing him to shoot free throws, which became a very effective and widely used tactic throughout the league. In fact, it was so effective that the last two minutes of every game would see the opposing team try to chase down Wilt in a comedic game of playground tag, all because Wilt wanted to spare himself -- and the sport for that matter -- the embarrassment of having to endure his free throw attempts.