Athletes peak at different ages, often depending on their style of play and the sport itself. Recent studies suggest that baseball players peak around 27-29, tennis players 23-26, basketball players around 27, soccer players 26-31, sprinters 22-25, and so on. In the vast majority of major sports, the peak age tends to be somewhere between 23 and 29, with exceptions such as golfers, quarterbacks in football and goalkeepers in soccer.

It is unsurprisingly rare for athletes to retire during their peak without good reason. Most athletes retire once they have begun to decline or already severely dropped in performance levels since their peak years. This list only features athletes who retired through choice, not through injury. The likes of Bobby Orr and Sandy Koufax, who retired far younger than many expected were still in their prime, but they retired through injuries, not their own decisions.

Furthermore, athletes who retired young but had dropped off in terms of form are also not included. For example, Bjorn Borg who retired at 26, or George Best who first retired at 27 were both far too young, but neither were in their peak at that time; both experienced their finest years earlier than that age. Lastly, some of these athletes did go on to make a return to sport following their original retirement, while others left the world of sport prematurely never to return. Here are the top 15 athletes who retired in their prime:

15 15. Pat Tillman

Pat Tillman spent three years in the NFL before leaving the league and sport behind in 2001 in the aftermath of the 9/11 terror attacks. While Tillman may not have been at the very top of his sport as many of the others on this list are, he was highly regarded within football and was certainly at the peak of his powers, aged just 24, when he enlisted to join the U.S. Army. Tragically, on April 22nd 2004, Tillman was reported to be dead. Originally, reports suggested enemy attack as the cause of death, but it was later revealed that Tillman died as a result of friendly fire.

14 14. Annika Sorenstam

Annika Sorenstam is one of the greatest female golfers in history. She had the third most LPGA tour wins in history and the fourth most majors. In total, she won 90 international tournaments as a professional, as well as holding the all-time LPGA record for earning's, having won $22 million throughout her career. Sorenstam retired in 2008, aged 37, citing her desire to start a family as her reason for retiring. That year she had won three LPGA events and was second in the scoring average, she was very much still in her prime.

13 13. Carlos Roa

Carlos Roa without doubt has the oddest reason for retiring of any of the athletes on this list. We can understand someone wanting to start a family or struggling with the pressures of top class sports, but Roa, a practising Seventh-day Adventist, retired in 1999 because he believed that the world was going to end imminently. Of course, it didn't, and Roa returned to soccer less than a year later. When he first retired, aged 30, he was at his absolute peak. He had been Argentina's no. 1 at the 1998 World Cup and played in a Cup Winners Cup with Mallorca in 1999. Following his return, he never returned to that level.

12 12. Bo Jackson

The man that ESPN named the greatest athlete of all time, Bo Jackson is the only athlete to be named an All-Star in two major American sports. Possibly the greatest two-sport athlete of the modern era, Jackson played in the NFL from 1987 to 1990, and the MLB from 1986 to 1994. At the time of his retirement from professional football in 1990, Jackson was only 28, and had just made the Pro Bowl for the first time in his career. While a hip injury was linked to his early retirement, Jackson also wanted to give more time to his other pursuits, including baseball, which he retired from aged 32.

11 11. Barry Sanders

After 1,491 rushing yards in the 1998 season, Barry Sanders only needed to repeat that number in the 1999 season to become the NFL's all-time leading rusher, a record held by Walter Payton. However, Sanders, a man who was widely expected to do just that, never had a 1999 season, choosing instead to retire from football, in a decision supposedly based upon his discontent with Detroit's growing reputation as a losing team. Outraged Lions fans and management demanded that Sanders return his $7 million sign-on fee, which he refused, and eventually had to after the Lions sued him.

10 10. Lorena Ochoa

Lorena Ochoa had just an eight year golfing career, remarkably short by any highly-successful athletes standards, and especially short given that golfers generally enjoy greater longevity than that of other sports. Ochoa became the number 1 ranked female golfer in the world in 2007, a position which she held until the day of her retirement in 2010, aged just 28. Ochoa was also the highest-paid female golfer in the world in the year of her quitting, but she claimed a short career was always her intention.

9 9. Bobby Jones

Perhaps the greatest amateur golfer in the sport's history, Bobby Jones dominated the amateur game throughout his career and regularly beat the top-ranked pro golfers of his time. Jones won the U.S. Open four times in a ten year career. He is the only man to complete golf's Grand Slam in a single season and won 13 of the 31 majors he ever entered. He retired at the premature age of just 28, after his greatest year and arguably the greatest year of any male player in history. There can be no doubt that Bobby Jones was very much in his prime when he called time on his golfing career in 1930.

8 8. Rocky Marciano

The only undefeated heavyweight champion of the world of all time, and the man who has the highest knock-out percentage of any heavyweight champion in history. With a record of 49 fights, 49 wins, 43 KOs, 0 draws and 0 losses, Marciano had every right to hang up his gloves at the age of 32, but it's a real shame for the sport that he did. His critics argue that Marciano didn't face a great deal of top class opposition, and that the top class fighters he did face were past their prime. Marciano's last fight in 1955 was a ninth round KO of Archie Moore, and he very much appeared to be in his prime.

7 7. Eric Cantona

Eric Cantona, affectionately referred to as 'King Eric' by many Manchester United fans, was one of the Premier League's all-time great players. A 2001 poll saw Cantona named Manchester United's greatest ever player, and while that was a little generous, he's certainly up there. Cantona certainly peaked later than most, possibly due to his game being more reliant on technical prowess and finesse than pace, but when he quit soccer at the age of 30, he was just about at the peak of his powers; he now works as an actor.

6 6. Mark Spitz

Mark Spitz won seven gold medals at the 1972 summer Olympics, setting world records in all seven, he remains the only man to do so in Olympic history. In total, Spitz won 9 Olympics golds, as well as one silver and one bronze. He retired following the 1972 games, aged just 22. When Spitz finally returned to swimming in an attempt to qualify for the 1992 games, he was 41 years of age, he missed out by only 2 seconds and came very close to his 1972 times, an indication of just how successful he could have been had he remained in swimming post-72. After Spitz's performances at the 1972 games, few could question that was him in his prime.

5 5. Ken Dryden

Perhaps better known today as a politician, Ken Dryden was at one time one of the finest NHL players around. Dryden made his NHL debut in 1971 and his final appearance in 1979, spending his entire professional career with the Montreal Canadiens. An extraordinary goaltender with an extraordinary record, Dryden lost only 57 of the games he played in, winning a whopping 258. He is quite rightly a hockey Hall of Famer despite retiring in 1979 at the age of just 31, when he was arguably at the peak of his powers.

4 4. Robert Smith

Robert Smith was a superb running back for the Minnesota Vikings, but how they wish he had stayed around a little longer. Smith made the 1993 draft and while his early career faced a number of difficulties, once he broke through in 1997 there was no looking back. He gained 1,266 yards in his breakthrough season of '97, but recorded his highest ever total in 2000, his final season in the NFL, with 1,521 yards. Smith retired in 2000 at the age of 28, he was truly at the peak of his powers. Despite such an early retirement, Smith still set the record for Vikings rushing yards, which has since been surpassed only by Adrian Peterson. He also holds the all-time NFL record for average yards per touchdown.

3 3. Mario de Castro

The most clinical striker in soccer history, Mario de Castro scored an incredible 195 goals in 100 games. It is a record which make him not only a legend of Brazilian soccer but also a legend of the sport itself, holding a record which could quite possibly never be beaten. His career lasted only five years - from 1926 to 1931 - but despite that he remained Atletico Mineiro's all-time top scorer until 1972.

He was never capped by Brazil after turning down an invitation to play for his country when he was told he would be on the bench. Mario de Castro retired in 1931 at the age of 26 after Atletico's club director shot an opposition fan, he was widely regarded as the best player in Brazil at the time and was, without question, at the peak of his powers.

2 2. Michael Jordan

The greatest basketball player of all time and one of the most recognizable athletes in all of sports history, Michael Jordan requires little introduction, so we shall keep it brief. A six time NBA champion, six time NBA finals MVP, five time NBA MVP, 14 time NBA All-Star and three time NBA All-Star MVP. Those are the stats which define Michael Jordan, the first billionaire athlete according to Forbes.

However, Jordan's stats could have been even more impressive had he not 'retired' in 1993. Following the murder of his father, Jordan retired from basketball to try his hand at baseball, as his father had always envisioned his son as a MLB player. His time in baseball was brief, and he returned to the NBA in 1995 to incredible success but one could certainly argue that in 1993, aged 30, he was in his prime. Could he have led he Bulls to eight straight titles?

1 1. Jim Brown

Regarded by most as the NFL's greatest ever running back, Sporting News even went as far as naming Brown as the greatest professional football player of all time. He was certainly the best player in the NFL when he decided to call it a day on his career. His NFL career lasted only eight years, remarkably short for a player of his caliber, and he spent all eight years with the Cleveland Browns.

Three-time NFL MVP and nine-time Pro Bowl selection, Brown retired as the NFL's all-time leading rusher. Brown was quoted as saying, "Make sure when anyone tackles you he remembers how much it hurts," and that mantra certainly did him well. He remains the Cleveland Browns all-time leading rusher and his 133 yards per game average in the 1963 season has only since been beaten by O.J. Simpson in the 1973 season.