Owners of teams in professional sports are in constant contact with each other, looking for players to improve their roster or to ship off a contract or player that has not proven their worth. When trades do happen, it can shift the entire landscape of the league and send teams and players in directions they would not have gone otherwise.

But what about when the trades don’t happen? Often in sports a deal is drawn up, even having the deal signed, just to see a player or GM have a change of heart and prevent the deal from happening. This changes the course of entire seasons and of the success a player may have. In a number of these instances, a team nearly traded an unproven young player who turns out to be a star for their franchise or the opposite also happens when a GM fails to pull the trigger on bringing in a young unproven player that turns out to be a difference maker.

As sports fans, we know that anything can happen. Literally. Here is a list of fifteen trades across sports that almost happened, but never came to fruition, allowing us to speculate what could have been.

15 15. Brandon Marshall to the New England Patriots

Before signing his three year contract extension with the Chicago Bears during the 2014 off-season, the Bears were actively shopping wide receiver Brandon Marshall and had a deal drawn up with the New England Patriots, according to The Chicago Sun Times. If the move had happened, maybe the relationship between Marshall and Bears quarterback Jay Cutler never would have soured and maybe the Patriots wouldn't have struggled to begin the year (we all know they turned it around). However, the move never happened and now Marshall can look forward to playing the Patriots twice a year as a member of the Jets.

14 14. Justin Verlander and Curtis Granderson for Dontrelle Willis

Before landing Miguel Cabrera a year later, the Detroit Tigers reportedly almost gave up a pitcher who became a Cy Young and MVP winner and one of the team's best players at the time for a declining Dontrelle Willis. The Tigers lucked out in holding on to Verlander and Granderson, because the following off season they still landed Willis in the trade for Miguel Cabrera. Who did the Tigers lose (of note) in that trade? Cameron Maybin and Andrew Miller. Willis never regained the form that helped him finish second in Cy Young voting in 2005 and the Tigers eventually traded Granderson, but they managed to keep a pitcher that dominated baseball for a few years.

13 13. Claude Giroux to the Tampa Bay Lightning

In 2009, Philadelphia Flyers GM Paul Holmgren almost traded away the team's future by nearly shipping then-rookie Claude Giroux to the Tampa Bay Lighting for defenseman Paul Ranger. Giroux, who was having an average season and had questions about his size translating the NHL level, was offered to Tampa Bay as the Flyers were desperate for some defensive help. Lightning GM Brian Lawton declined the trade, as he admitted on Sportsnet, and held on to a player that stayed in the league for just eight more games, leaving the Flyers with a franchise player.

12 12. Albert Pujols

While still a young prospect, Albert Pujols was nearly traded to the Montreal Expos for peanuts. Pondering between sending third baseman Fernando Tatis or Albert Pujols away as they had a logjam at the position, the Cardinals inevitable moved Tatis for a pair of relatively unknown pitchers. The following year, Pujols won the MLB Rookie of the Year award and enjoyed an eleven-year tenure with the Cardinals that included three MVPs and two World Series rings. It's entirely possible that the Cardinals wouldn't have won those World Series rings if they moved Pujols.

11 11. John Elway to the Washington Redskins

During the 1991 off-season, The Redskins were looking to upgrade their quarterback position, to get over the hump and win a Super Bowl trophy. They didn't feel Mark Rypien was an elite QB and were looking to move for Elway. However, the Broncos insisted on receiving offensive lineman Jim Lachey in any deal with the Redskins, according to The Washington Post. Not wanting to give up the player most likely to protect their quarterback, the Redskins backed out and went on to win that season’s Super Bowl with Rypien, while Elway and the Broncos waited six years before getting their Lombardi Trophy.

10 10. Scottie Pippen to the Seattle SuperSonics

In a move that ultimately could have affected the way we view Michael Jordan today, the Chicago Bulls almost sent Scottie Pippen to the Seattle SuperSonics for power forward Shawn Kemp. During the offseason in 1994, while Jordan was on a hiatus to play baseball, the Bulls were in talks with the SuperSonics to send Pippen to Seattle for Kemp and Ricky Pierce, as well as swapping first rounders, according to the Chicago Tribune. The deal never happened and when asked if His Airness would have returned to the NBA had Pippen been traded, Jordan responded “Probably not. I could have played with Shawn, but I wouldn't have been as comfortable as I was with Scottie.”

9 9. Steven Stamkos to the New York Rangers

Before passing up on Claude Giroux, Tampa Bay Lightning GM Brian Lawton made possibly an even more important franchise saving move, shooting down team owner Len Barrie’s trade agreement with Rangers GM Glen Sather. That would have sent Steven Stamkos to the New York Rangers for a package that could've included Ryan Callahan, Brandon Dubinsky and Michael Del Zotto, according to The New York Post. Amidst a poor start to his rookie season, Stamkos, arguably the best goal scorer in the leagu,e was almost shipped off before his career got started. Though the Lightning would have received some solid players, I think they are much happier having one of the league's best players.

8 8. Charles Barkley to the Los Angeles Lakers

Back in 1993, Charles Barkley was actually a Laker for about two hours. After being told of the good news, the Philadelphia 76er went out to celebrate by having a few drinks, only to be informed by his agent a few hours later that the deal, which would send Barkley to L.A. for James Worthy, was off, according to SBNation. Barkley would eventually be traded to the Phoenix Suns for Jeff Hornacek. The Suns made the playoffs and gave Michael Jordan’s Bulls a run for their money in the 1993 NBA Finals. The Lakers however were amidst a dry spell that didn’t see a playoff appearance until 1995, the year after Worthy retired. And the Sixers were still busy being the Sixers.

7 7. Mariano Rivera to Detroit Tigers

At the beginning of Mariano Rivera’s rookie season, he was a part of the New York Yankees starting rotation. In just 67 innings of pitching, Mo gave up 11 home runs and had an ERA of 5.51. The Yankees offered up the young prospect to the Detroit Tigers for proven veteran David Wells, according to The Detroit News. After showing signs of improvement on his fastball, Rivera was pulled off the trading block and moved to a relief role on the Yankees pitching staff. Baseball’s most dominant closer posted an ERA of 2.09 as a reliever the following season, was eventually tabbed as the closer and the rest is history.

6 6. Aaron Rodgers for Randy Moss

While Brett Favre was still running the show in Green Bay, the Packers tried to shop their promising backup quarterback Aaron Rodgers for some offensive weapons to help the aging Favre. The Raiders were actually the ones to shut down this trade because they wanted a first-rounder for Moss, bu tThe Packers only wanted to exchange Rodgers, according to Inside The Bay Area. This trade could have revitalized the Raiders franchise, while the Packers would have been forced to deal with Favre waffling every year and they probably would not have won the Lombardi Trophy in 2010. On top of that, Moss would not have ended up in New England to break all those records with Tom Brady.

5 5. Kobe Bryant to Chicago Bulls

In a trade that would have shaken up the entire landscape of the NBA as we currently know it, the Los Angeles Lakers nearly sent an unhappy Kobe Bryant to the Chicago Bulls. In return the Lakers would have received Joakim Noah, Tyrus Thomas, Luol Deng and Ben Gordon, according to NBC Sports. Bryant, sick of playing with players like Smush Parker and Kwame Brown, refused the trade if Chicago didn't keep Deng, since Kobe had no desire to leave a talent-less team to play for another. He also apparently vetoed a trade to the Pistons at the same time. Had these two teams worked this trade out, the Lakers may have never won their two latest championships, the Bulls probably never would have drafted Derrick Rose, and everything we know as basketball fans would be different.

4 4. Ralph Sampson for Michael Jordan and Clyde Drexler

The Houston Rockets could have been the originators of the “Big 3” in the NBA had the trade they attempted with the Portland Trail Blazers went down. In 1984, the Rockets tried to trade away Ralph Sampson (a future Hall of Famer) for the second overall pick in the draft, according to Bleacher Report. Already owning the first pick, the Rockets would have been able to select Hakeem Olajuwon and Michael Jordan 1-2 in the 1984 NBA Draft. Oh yeah, the trade also would have given the Rockets, Clyde “The Glide” Drexler.

3 3. Miguel Cabrera to the Los Angeles Angels

Imagine a lineup that would have Mike Trout and Miguel Cabrera hitting back to back? Well, it nearly happened. Back in 2007, when the Florida Marlins were shopping the 24-year old Venezuelan before he became a free-agent the following season, the Angels had nearly completed a deal that would have landed the young slugger. However, since the Marlins wanted to dump Dontrelle Willis and his contract, the Detroit Tigers stepped in and said “sure, we'll take Willis, ” according to MLB.com. So, the Marlins shipped Miggy to Detroit. Though Cabrera has been successful as a member of the Tigers, it would be fun to watch these two battling for MVPs in the same uniform.

2 2. Chris Paul to the Los Angeles Lakers

In one of the more controversial trade halts in sports history, NBA commissioner David Stern prevented the league owned New Orleans Hornets from completing a three team trade that would have sent Chris Paul to the Lakers and Pau Gasol to the Houston Rockets. The Hornets would have received a nice care package of Goran Dragic, Lamar Odom, Luis Scola, Kevin Martin, and the Rockets first-round pick the following year. Stern stated that the reason for the stop was he was pressured from the other owners to nix the trade to maintain competitive balance, it has however been documented that many NBA owners state the decision was completely Stern’s.

1 1. A-Rod to the Boston Red Sox

After the gut wrenching game game 7 loss to the Boston Red Sox at the hands of Aaron Boone, the Red Sox were desperate to improve their roster to be sure not to have the same fate the following year. Theo Epstein completed the deal with the Texas Rangers and Chicago White Sox that would have seen them land Alex Rodriguez along with Magglio Ordonez and pitcher Brandon McCarthy, while they'd be giving up Manny Ramirez, Nomar Garciaparra, and a young Jon Lester. The deal was signed by A-Rod and he was set to wear a Red Sox uniform. However, the deal never passed the MLBPA, siting that Rodriguez was taking too much of a pay cut and he was still a Ranger, according to The Boston Globe.

In a twisted series of events, Boone, who had already stabbed the Red Sox in the heart, decided to twist the knife by injuring his knee in a pickup basketball game and leaving the Yankees without a third baseman. A-Rod announced he was willing to make the move to third base and the Yankees stole the Red Sox guy. In the end, it turned out that the Red Sox dodged a bullet, as they went on to beat A-Rod’s Yankees by overcoming a historic three game deficit the following year and winning Boston’s first world series in 86 years. On top of that, we all know what has become of Rodriguez and the Yankees.