As the Yankees try to sort out their pitching lineup for the year, manager Joe Girardi announced yesterday that 22-year-old Joba Chamberlain won’t be in the starting role that Hank Steinbrenner noisily projected for him not so long ago. Instead, he’ll stay on as Mariano Rivera’s set-up man. “We think that’s where he fits best right now,” explained Girardi. “He’s a back-end guy. That’s how I’m going to classify him.” After all the meticulous care that went into his playing last year as he opened for Mariano Rivera, this is new territory. “There are no restrictions, just common sense,” Girardi said. But is Joba shaken by the news? “I had an idea if everybody stayed healthy this would happen,” he said. “It’s best for the team right now. It’s about winning games. It’s not about Joba Chamberlain.” Aw, Joba! That’s so sweet! And wrong. Now that the kid-gloves treatment has stopped, it’s going to be near impossible to keep up your stellar record from last year. Since fan expectations are so high, if you trip up, we’re guessing it is going to be all about Joba Chamberlain. And maybe not in a good way.