Borg's most ardent followers mourn what could have been had he not quit for the first time at 26 then slogged through several failed comebacks. They insist he's the best male tennis player ever, not Roger Federer. But Borg's actual Grand Slam total puts him squarely in the middle of the pack with Rafael Nadal, Pete Sampras and Rod Laver. Even his projected total of four to five more, had he played on, still leaves him shy of Federer, who has won 17 majors so far and may have one or two more Slam titles in him. (Projection made by tennis analytics expert Benjamin Tom by hypothetically extending careers to match the trends displayed by other Grand Slam champions who had full careers.)

( NHL ) Mario

Lemieux One of the most skilled and artful players in hockey history, Lemieux missed the better part of three seasons battling back injuries and Hodgkin lymphoma. Then he retired at age 31 in 1997, frustrated as the NHL trended toward clutching and grabbing over skill and playmaking. At Lemieux's peak, he was a more prolific scorer than even Wayne Gretzky, and he returned to the NHL in 2000 and played in parts of five more seasons. By virtually restoring those lost years, Lemieux projects to climb to No. 2 on the NHL's career goals and points list and No. 3 in assists. (Projections made by ESPN.com Insider Rob Vollman.) ( NFL ) Jim

Brown While it was a shame to see the reigning MVP retire at age 30 prior to the 1966 season, he likely had only one big year left in the NFL. Running backs generally decline in their 30s, and this was even more true in the 1960s. In that entire decade, John Henry Johnson was the only back to play significant time after age 31. Brown also would have shared carries more and more each year with rising star Leroy Kelly, a fellow Hall of Famer who was just 24 when Brown retired. (Projections made by Aaron Schatz of Football Outsiders.) ( NFL ) Barry

Sanders Sanders likely would have lasted longer than Jim Brown, as the top running backs were more likely to play into their 30s in the 1990s than the '60s. But not much longer. Marcus Allen was the only contemporary of Sanders who was effective long after turning 33. It's also unlikely a 30-something Sanders would have rebounded from the big drop in yards per carry between his legendary 1997 season (6.1) and his more pedestrian final season in 1998 (4.3). Interestingly, according to the projection, Sanders' career rushing total would have fallen 3 yards short of Emmitt Smith's NFL record. (Projections made by Aaron Schatz of Football Outsiders.) ( Tennis ) Monica

Seles The hard-hitting Seles was a brilliant, enigmatic presence who won her first Grand Slam singles title at 16 and had eight by her 20th birthday. She eclipsed Steffi Graf for No. 1 in 1991 and '92 and had nearly leveled their terrific head-to-head rivalry at 4-5 when a deranged fan of Graf's stabbed Seles in the back during a match changeover in Hamburg, Germany. Seles missed two years and was never the same. Given her 3-1 record against Graf in Slam finals, Seles' projected total of 15-16 Slams seems reasonable. So does the argument that Graf wouldn't have gotten 22 major titles had Seles not been harmed. (Projection made by tennis analytics expert Benjamin Tom by hypothetically extending careers to match the trends displayed by other Grand Slam champions who had full careers.) ( MLB ) Kirby

Puckett Puckett is one of the most beloved athletes ever in Minnesota, a 10-time All-Star who helped lead the Twins to World Series championships in 1987 and 1991. Although his career was cut short by glaucoma at age 35, he still earned induction to the Hall of Fame on the first ballot in 2001. If we turn back the clock and grant a healthy Puckett six more seasons, he projects to eclipse the 3,000-hit plateau and approach 1,500 RBIs. (Projections made by ESPN.com's Dan Szymborski. Rankings through Monday's games.) back to top More Stories