Derek Jeter says he’ll be just fine, plate and screws in his left ankle notwithstanding. And we should know by now not to doubt him, after he led the majors in hits in 2012, only a year or so after even some of the most sage scouts in baseball were convinced he would never hit .275 again, never mind .316. Yet I’m not convinced that he knows exactly what he’s in for trying to play shortstop at age 39 — as of June 26 — while on the comeback from that broken ankle suffered last October. And here’s the scary part for the Yankees: With all of their questions about age and injury, they almost certainly need Jeter to play at, or close to, the level he did last season to have any real shot at being a championship-caliber ballclub. The effect of the ankle injury sure seems to make that less than likely. Jeter will love this, of course. He takes any such speculation as a personal slight and uses it to drive him on a daily basis. As his old buddy, Jorge Posada, once told me, with a bit of a chuckle: “Derek looks for reasons to prove people wrong.’’ So we’ll see. Jeter seemed to be in great spirits on Sunday, meeting the media at his annual spring training-arrival press conference. For someone who almost always dismisses injury questions during the season, the Captain was expansive in discussing the “absolutely terrible’’ offseason he endured while recovering from the broken ankle. Read more: