Disagreements are quite common in sports. That's one of the ways that athletics builds character, by teaching participants to channel their energy towards performing well instead of initiating confrontations with the other team.

Of course, if it was easy to accomplish that, then there would never be altercations on the field or court. Sadly, these types of incidents can be found at all levels - from the elite professional leagues all the way down to pickup games. And sometimes, things can get physical.

That said, these disputes are often magnified in the world of professional sports. First, teams usually play each other every year (except in the NFL), so that rivalries and grudges are rekindled frequently. And when you take men who may not have mastered the nuances of communication, and mix them in with media outlets who love to imply meanings, exaggerate statements, and stoke discord; you've got a recipe for full-blown animosity to develop - some of which can turn nasty.

But it's quarreling among players on the same team that can potentially be the most destructive. Not only can they impact the in-game results of the individuals involved, but it can also split the team into factions and erode the performance of the entire squad. In short, teammate feuds can be incredibly cancerous to the well-being of a franchise.

It's not hard to see how these feuds can develop. You have dozens of highly self-motivated people who place a strong emphasis on victory instead of compromise. They tend to be concerned about how they are viewed by others, and they may even have a public image to maintain that translates into endorsement deals. When you make these athletes battle each other for playing time and then expect them to work together as a team, disputes will inevitably develop. And when these people are placed in close quarters for months at a time, it doesn't take much for a spark of negativity to ignite into a full-blown conflict.

Here are the twenty worst feuds among teammates in history. We're going to be looking at feuds that took place during the time on the same roster, so TO and McNabb aren't going to make it.

20 20. Johnny Evers and Joe Tinker - Chicago Cubs

Baseball geeks might have heard of a poem entitled "Tinker to Evers to Chance," which waxed about the 6-4-3 double-play combination of the Chicago Cubs (along with first baseman Frank Chance) in the early 20th century. All three of them are now in the National Baseball Hall of Fame. But you may not know that the shortstop and the second baseman thought so little of one another that they reportedly ceased speaking for 33 years. The reason? A dispute over a cab fare in 1905.

19 19. Delonte West and Von Wafer - Boston Celtics

West has cemented a reputation for being somewhat of a "head case" in the NBA. He stuck a finger in Gordon Hayward's ear during a game, and was suspended indefinitely by the Dallas Mavericks in 2012. But a couple years before that, West had gotten into hot water with the Celtics for his attitude. In October of 2010, West was guarding Wafer in a 3-on-3 game and kept fouling whenever Wafer touched the ball. Wafer left the court mid-game and showered in the locker room. West reportedly snuck up behind him and threw a punch, and the two began wailing on one another until being separated.

18 18. Robert Baker and Noel Prefontaine - Toronto Argonauts

The CFL's Argos had called itself a "family," but some sibling rivalry emerged during a July 2005 game against Calgary. After Baker became enraged reportedly because a Stampeder player spit on him, he had to be pulled off the field by his coach. For some reason, Prefontaine (the team's kicker) decided to get into Baker's face about it on the sideline, prompting Baker to slug him in the face. The team subsequently suspended the wideout for Toronto's next game.

17 17. Peyton Manning and Mike Vanderjagt - Indianapolis Colts

Speaking of kickers… Vanderjagt forever became known as the Colts' "idiot kicker" after Manning tagged him with that moniker in an interview during the 2003 NFL Pro Bowl. A few weeks before that, Indy had been trounced 41-0 in the playoffs by the New York Jets, prompting Vanderjagt to call out his team's QB and head coach Tony Dungy in a Canadian TV interview for not being fiery enough leaders, adding, "I just don't see us getting better." Four years later, Vanderjagt was released mid-season and left the NFL forever, and Manning led the Colts to a win in Super Bowl XLI (while earning MVP honors for the game).

16 16. Ruben Patterson and Zach Randolph - Portland Trail Blazers

Remember the Jail Blazers? The club always seemed to be crossing paths with the police blotter about a decade ago. So when former juvenile delinquent Randolph and accused domestic abuser Patterson crossed paths on the practice court in 2003, the result was predictable. When Patterson got into an argument with fellow Blazer Qyntel Woods, Randolph stepped in and tagged Patterson in the face. Randolph received a $100,000 fine and a two-game suspension from the NBA.

15 15. Kevin Garnett and Wally Szczerbiak - Minnesota Timberwolves

Here, you have an NBA star who expects strong defense from himself and his teammates, and an offensive-minded guy who wasn't known for his defensive prowess. During a T-Wolves practice in 2000, Sczerbiak reportedly expressed his displeasure at Garnett for not calling out a screen during a play, and Garnett retorted by telling Sczerbiak to "play some defense." An hour after practice in the training room, Garnett had to be restrained after approaching Sczerbiak to "discuss" the matter.

14 14. Steve Downie and Akim Aliu - Windsor Spitfires

This dust-up was especially disgusting because it came amid allegations of player hazing. Once Aliu was signed by Windsor of the Ontario Hockey League, he was allegedly ordered to strip naked and stuff himself into a bus bathroom along with other rookie Spitfire players. Aliu refused, which earned him the ire of many of his teammates. Weeks later, the captain Downie cross-checked Aliu in the mouth during a practice and left the ice - only to come back and start a fight with the rookie. Downie was suspended five games by the club and ordered to undergo anger management.

13 13. Charles Barkley and Scottie Pippen - Houston Rockets

A couple of former dominating NBA players stuck on the same team well after their prime? What could possibly go wrong? Barkley and Pippen played together in the strike-shortened season. But prior to the 1999 preseason, Barkley told the media that Pippen owed the team an apology for engaging in trade talks with the Lakers. Pippen later responded by saying he wouldn't apologize if he had a gun to his head, and that Barkley was selfish, undedicated, and had a "fat butt." Pippen soon was traded to Portland, while Barkley left the league after the following season.

12 12. Bill Romanowski and Marcus Williams - Oakland Raiders

It's rare that a teammate feud actually becomes intense enough to end a career. But that's what happened in August of 2003 during an Oakland preseason scrimmage. Romanowski, whose name was synonymous with "roid rage," took exception to how Williams was holding him during a play. So the linebacker ripped off Williams' helmet and punched him in the eye. The blow fractured the tight end's orbital bone, and Williams was eventually waived and never played football again. Believe it or not, Williams actually received $340,000 in a civil lawsuit against Romanowski in 2005.

11 11. Jimmy Jackson and Jason Kidd - Dallas Mavericks

Along with Jamal Mashburn, Kidd and Jackson were supposed to kickstart the struggling Mavs' franchise in the mid-1990s. But Kidd accused Jackson of being selfish on the court, and the two never really got along during their 2 1/2 seasons in Dallas. A juicier reason for their feud came from a rumor involving singer Toni Braxton, who apparently showed up at an Atlanta hotel for a date with Kidd but left with Jackson instead. Both men have denied the story.

10 10. Fernando Alonso and Lewis Hamilton - McLaren F1 Racing

No, auto racing is not an individual sport. Almost any driver will tell you that. It takes a strong team to be successful in Formula One, which is partly why racing teams have multiple drivers. Alonso joined the McLaren family in 2007 after winning two consecutive F1 titles, and Hamilton was signed as a rookie. But the two began butting heads early in the '07 season, and they began bad-mouthing each other in the press. The row culminated at the Hungarian Grand Prix, where Alonso refused to move his car in the pits to allow Hamilton to take another qualifying lap. Both drivers stopped speaking to each other for the rest of the season. Hamilton went on to win the 2008 title, while Alonso left McLaren.

9 9. Don Sutton and Steve Garvey - Los Angeles Dodgers

How could a couple of Dodger all-time greats not be locker room buddies? Pretty easily, in fact. The two were generally cool to one another until Sutton made some quotes in a Washington Post article in 1978. He said that despite Garvey's media popularity, it was teammate Reggie Smith who had "carried" LA for the previous two years, but that no one was aware of that because Smith didn't have a "Madison Avenue image." When Garvey confronted Sutton in the clubhouse later, Sutton confirmed the comments - and Garvey slammed him up against a row of lockers. Both players ended up with cuts and bruises. Even though they parted ways in 1980, Sutton later hit Garvey in the head with a pitch in a spring training game in 1984. Garvey later hit a line drive right back at Sutton.

8 8. O.J. Mayo and Tony Allen - Memphis Grizzlies

Non-sports fans may find in hard to believe that one of the biggest catalysts for disagreements among NBA players is card games. Such was the case on the second day of 2011 when the Griz were flying back home after a game. Mayo reportedly had refused to pay a $7,500 debt he owed to Allen in a card game, and then proceeded to berate his teammate. Mayo continued running his mouth, criticizing Allen's game and bragging that he was a better player than Allen. After about 15 minutes, Allen had had enough - so he punched Mayo several times in the face.

7 7. Carlos Zambrano and Michael Barrett - Chicago Cubs

In 2007, the Cubs were in the midst of another woeful stretch on the first day of June, having lost four straight and 10 of 14. In the fifth inning of a matchup with Atlanta, starter Zambrano gave up five runs on five hits, while catcher Barrett allowed a passed ball and made a throwing error on the same play. After the inning, Zambrano approached Barrett in the dugout and shouted at him, Barrett responded, and the two scrapped for a bit before being separated. Zambrano was pulled from the game, and Barrett suffered a cut lip. A disgusted manager Lou Piniella said after the game, "It's about time some of them started playing like Major Leaguers."

6 6. Kieron Dyer and Lee Bowyer - Newcastle United

It's rare to see soccer players actually fight each other during a game - much less two players on the same side. That's what happened in 2005 in a Newcastle loss to Aston Villa. As told later by Dyer, Bowyer was upset about not being passed the ball, and Dyer responded with an expletive. Bowyer grabbed his teammate and started punching him, and the two were separated by the referee and both given red cards. Here's the best part: in the dressing room, they were about to continue the scrum but stopped when manager Graeme Souness threatened to fight them both.

5 5. Barry Bonds and Jeff Kent

Put two "challenging" personalities in the same baseball clubhouse, and you're likely to have a feud. Bonds and Kent's dislike for each other was an "open secret" for about five years until June of 2002. During a game in San Diego, Kent was apparently criticizing infielder David Bell when Bonds stuck up for him. The two began shoving each other before being pulled apart, and Kent was heard to say that he wanted to leave the team. Not even a Giants' World Series appearance would keep Kent in San Francisco, as he was traded to Houston in the offseason.

4 4. Michael Westbrook and Stephen Davis - Washington Redskins

This particular grudge was kept under wraps from most of the team for a couple of years before it came to a head in August of 1997. During a non-contact training camp workout, Davis allegedly called Westbrook a pejorative name for a homosexual. In front of TV cameras, Westbrook was seen standing over Davis and pounding him. Davis suffered facial injuries and Westbrook was fined $50,000 by the club. Westbrook later apologized for the incident.

3 3. Darryl Strawberry and Keith Hernandez - New York Mets

Some fights spring up during the heat of battle on the field. But you know that two guys don't like each other when they attack each other on team photo day. It happened in spring training of 1989, when Strawberry reportedly didn't want to sit next to Hernandez in the picture and Hernandez took exception. A few curse words later, Strawberry threw a punch at Hernandez, and the whole team had to separate the two combatants. Strawberry was reportedly angry that Hernandez didn't support him during an earlier contract dispute with the team.

2 2. Shaquille O'Neal and Kobe Bryant - Los Angeles Lakers

Unlike many other entries on this list, this feud wasn't defined by any single incident. Rather, it slowly metastasized over the eight years the two superstars shared a locker room together. It began in 1996 when Bryant was signed out of high school and O'Neal was inked to a free agent contract. Shaq thought Kobe was selfish and arrogant, and Bryant felt O'Neal was out of shape and a bad leader. Not even three NBA titles could warm relations between the two, and Shaq was traded to Miami after the 2003-04 season.

1 1. Gilbert Arenas and Javaris Crittenden - Washington Wizards

The reason that this dispute tops the list? One word: firearms. Again the flashpoint involved a card game in December of 2009, when Crittenden allegedly refused to pay a debt he owed to another player. When Arenas tried to intervene in the argument, Crittenden reportedly hurled an expletive and a slur at him, and both players threatened to shoot each other. The following day, Arenas, and then Crittenden, brandished guns in the Wizards locker room. No shots were fired, but both men were subsequently suspended for the rest of the season, and Crittenden never played in a regular season game again.