There comes a point in every ballplayer’s career when he senses the horizons dimming, especially when an injury refuses to heal. Joe DiMaggio, quiet and tough, knew the end was near in 1949 when bone spurs in his foot cost him half a season. He was done by ’51. Now Derek Jeter is at a similar crossroads. No matter what he says to the contrary, the Yankees captain has surely considered the possibility his best days are behind him. Jeter is hurt – again – which means he may have even played his final game. If so, the sport is already diminished. Only the most naive followers failed to grasp the severity of Thursday’s announcement — that Jeter had suffered yet another fracture in an ankle that was refurbished by surgeons last fall. The Yankees say Jeter will be out until the All-Star break, but team officials know better than to count on the shortstop’s return in 2013. They’re hoping for the best, of course, but prepared for the worst. That means acknowledging Jeter’s body is no longer capable of fully repairing itself, not with an injury this complex. The shortstop, who broke his ankle during the AL Championship Series last October, failed to make significant progress in spring training. He was left behind in Florida as the Yankees started the season in the Bronx and then refractured the ankle this week in Tampa, doing nothing more strenuous than taking ground balls. That’s the red flag Jeter must be fearing. At least there are no plans for surgery this time. The break, although significant enough to halt Jeter’s rehab program, is nevertheless small. Doctors say it can heal on its own. For the next four to eight weeks, Jeter will have time to reflect on his brilliant career, although his savage, competitive gene won’t allow him to concede defeat. But any logical person has already calculated Jeter’s long odds. It’s not unreasonable to think Jeter’s soon-to-be 39-year-old bones have said: enough.