Zack Wheeler is now a full-fledged Met. The prized pitcher strained his right oblique yesterday taking swings in the batting cage. These things just seem to happen to the Mets. Wheeler was scheduled to make his first Grapefruit League start against the Cardinals and face Carlos Beltran, the man he was traded for in the big deal that has given the Mets new life. But it seems like there’s always something with the Mets. The right-hander was coming off an impressive opening performance and already has won over the clubhouse with how respectful he is, and here is another example: Wheeler walked into manager Terry Collins’ office and apologized for getting hurt. “I told him there is nothing to apologize for,’’ Collins told The Post. “Those things happen. This kid is such a great kid, he knows what it is all about.’’ The Mets are trying their best to protect their young players and have told prized catcher Travis d’Arnaud there will be no blocking of the plate. But you can only do so much. Stuff happens. As for hitting in the cage on a day designated hitters were being used in the game, well, Mets pitchers work on their hitting. That’s the way it is. “People ask why is he hitting — because he’s a National League pitcher and they have to practice. That’s all part of the game in our league,’’ Collins said. “R.A. Dickey took extra hitting almost every day in a cage by himself. That’s what it is in the National League. We got to run the bases too, and there are going to be times when someone pulls a hamstring.’’