Want-to-be Cardinals starter Trevor Rosenthal didn’t miss many chances at last month’s Winter Warm-Up and baseball writers’ dinner to tweak manager Mike Matheny of his desire to one day take his leave of the bullpen, where Rosenthal has become an instant star. “I’ve got to give him a hard time,” joked Rosenthal after an informal workout here Tuesday, a day ahead of the club’s official reporting date for batterymen. “I’m excited to have a position, really, at this point,” said the 23-year-old Rosenthal. But, he appears gradually to be warming to this closer thing and doesn’t seem to mind being in it for the long haul. “To have an opportunity to do that for a long time would be pretty special,” said Rosenthal. “Starting would be a different challenge. Coming into the organization, I always kind of envisioned that being the end result. “Not that the bullpen is any worse. It’s just kind of the picture I’ve always had — of having an opportunity to be a starter like Chris Carpenter. He’s a guy I grew up looking up to and watching him pitch amazing games. “But having an opportunity to pitch in a World Series game (as a reliever) was a pretty cool thing, too. To have that adrenaline and to come in and to have the chance to close things out and be the last guy standing is cool.” And, in theory, profitable. “At the end of the day, it’s not about money,” said Rosenthal. “It’s what’s best for the team. The bullpen is a whole different thing. And it’s an awesome challenge. “From the day I got called up, when they told me, ‘Hey, you’re going to St. Louis,’ I was like, ‘What day am I starting?’ But it’s just one of those things you do to help out a team, like a Matt Carpenter going to play second (base), versus playing third, or whatever’s comfortable. You’re just doing what they ask of you. You’re just happy to be in the lineup.” After conditioning himself to be a starter last spring, Rosenthal was told near the end of camp, even before 2012 closer Jason Motte suffered a season-ending elbow injury, that he would be going to the bullpen. The process will be different this spring.