Mariano Rivera is getting close to moving from simulated games to actual exhibitions. “Maybe a [spring training] game,’’ Rivera said when asked what was next for him. “But I have to wait for the boss.’’ That would be the Yankees committee of trainer Steve Donahue, pitching coach Larry Rothschild and manager Joe Girardi. “I’ll talk to Mo and I’ll talk to Larry,” Girardi said. “It’s OK with me. I’m just kind of letting him go at his own pace. He’s been doing it for a long time.” Rivera worked an inning in a simulated game on the back field at George M. Steinbrenner Field yesterday in 45-degree weather. He threw 21 pitches in his second, and possibly last, simulated game. As has been the case since Rivera started working back from last June’s right knee surgery, he looked smooth and sharp. “How do you throw that thing?’’ Matt Diaz shouted at Rivera after flailing at a cut fastball. Andy Pettitte worked two simulated innings and finished with 34 pitches. Rivera is looking forward to facing hitters who aren’t Yankees, but figures he has waited this long, so he can hang on a little bit longer. “I have waited for 10 months, I can wait a few more days,’’ Rivera said. “I feel really good, my pitches are right where I want them,’’ Pettitte said following his first simulated game of camp. “Hopefully, keep my mechanics going.’’