Superstar slugger Giancarlo Stanton could be on the verge of signing the richest contract in the history of American professional sports. While the Miami Marlins might be smart to lock up one of baseball’s best hitters, recent history shows that the club could regret it in the long run.

The same day Stanton finished second in the National League MVP voting, ESPN reported that Miami and the outfielder were discussing a contract that could be worth $300 million over 10 years. Ken Rosenthal of Fox Sports reported on Friday that the two sides were talking about a 12-year deal worth approximately $320 million.

Entering his sixth MLB season, Stanton won’t be eligible for free agency until after the 2016 season. Stanton made $6.5 million in 2014, and he’s projected to make $13 million in arbitration in 2015. While the 25-year-old is under Miami’s control for the next two seasons, the organization is adamant about keeping their franchise player for the next decade.

A $300 million contract would surpass deals signed by Miguel Cabrera, Alex Rodriguez, Robinson Cano and Albert Pujols. It’s too early to grade the contracts signed by Cabrera and Cano last offseason, but the offers given to Rodriguez and Pujols have proven to be regrettable decisions.

Not only was Rodriguez's contract in 2008 for 10 years and $275 million an MLB record, but the deal has also turned out to be possibly the worst in sports history. With three years remaining, it’s  not known whether Rodriguez can still be a productive, everyday player. He hit just .244 in 44 games in 2013, and missed all of 2014 because of a suspension for performance-enhancing drugs. Since 2008, Rodriguez has hit just 57 home runs.

Pujols remains a valued MLB player, but he’s no longer close to being the best player in baseball. In three years with the Los Angeles Angels, the first baseman has no All-Star appearances and no playoff wins, recording the three lowest OPS numbers (.859, .767, .790) of his career. Pujols will begin the 2015 season at 35 years old, with seven years and $189 million owed to him.

Unless Miami ownership plans on opening its checkbook and spending a lot of money on free agents, Stanton will account for an unusually large portion of the team’s payroll. If Stanton had made $26.6 million in 2014, which is what his average salary would be in the proposed 12-year contract, his salary would’ve made up 43 percent of the Marlins’ payroll.

Zack Greinke was the highest-paid player in the 2014 season, and he accounted for 11.6 percent of the L.A. Dodgers’ payroll. Joe Mauer led all players, accounting for 27.1 percent of the last-place Minnesota Twins’ payroll. Four teams had one player make up more than 20 percent of their payroll, and none of them made it to the postseason.

The Marlins are usually near the bottom of the league in payroll, though they have spent money in the past. After a few major signings in 2012, the Marlins ranked seventh in MLB with over $118 million of combined player salaries. That didn’t last long, however, as the team traded a few of their top stars and cut the payroll to $46 million, following a 69-win season.

Stanton’s record-breaking contract could approach the value of the entire team. Before the start of last season, Forbes estimated the Marlins’ value at $500 million, and the club isn't showing many signs of increasing its worth. The Marlins finished last season 19 games out of first place and 27th in the league in attendance, with an average of 21,386 per game.

If any player deserves such a large contract, though, it appears to be Stanton. He’ll be just 25 years old through all of next season, and he led the NL with 37 homers and a .555 slugging percentage in 2014. Stanton has missed 102 games over the past three seasons because of injuries, though that includes a fluke injury when he was hit in the face with a pitch. In five seasons, Stanton has a career on-base plus slugging percentage (OPS) of .904 with 154 home runs.

Miami is hoping that Stanton rewards them for giving him a nine-figure contract, like both Mike Trout and Clayton Kershaw did with their respective teams in 2014. In the season after signing their mega-deals, the two L.A. stars won the 2014 AL and NL MVP awards. Unlike Rodriguez and Pujols, Trout (22 years old) and Kershaw (25 years old) were both under 30 when they signed their deals.