When Zack Wheeler is throwing his curveball for strikes, especially early in counts to make his 96-mph fastball all the more effective, he still profiles as that front-of-the-rotation starter the Mets envisioned before all of the down time the last three years. On Wednesday, Wheeler did just that, and his outing here against the Yankees was impressive enough to force the Mets’ decision-makers to at least consider re-thinking their plan for the starting rotation. Which is another way of saying: Steven Matz is on the clock. Mickey Callaway isn’t about to say that, of course. After Wheeler’s strong start on Wednesday, which the manager found impressive, he deflected questions about the starting rotation, saying “we have a battle going” that includes the likes of Seth Lugo and Robert Gsellman. In truth, though, only Matz is vulnerable so far among those who slot in behind Jacob deGrom and Noah Syndergaard, namely Matt Harvey and Jason Vargas, and with Opening Day three weeks away, the lefty from Long Island needs to start pitching well as soon as Friday against the Tigers. Ideally the Mets prefer to start the season with Matz in the rotation, but two poor starts have raised questions about his command and, perhaps more significantly, his confidence. It’s no small matter after Matz’s struggles last season, which translated to a rather hideous 6.08 ERA over 13 starts. Whether it was related to the need for nerve transposition surgery in his elbow or not, Matz so far looks tentative, to the point where Mickey Callaway told me the lefty needs to get over a mental hurdle. “He’s so worried about results that he’s not committing to the pitch,” Callaway said a couple of days ago.