On a day when they lose starter Andy Pettite for two weeks, the Yankees appeared to avoid another calamity when catcher Chris Stewart received a clean MRI on his left groin. Stewart “felt a grab” while running the bases on Thursday, he said. But no injury could be found. He’ll rest for a few days, with Austin Romine as the starter. Stewart is available as a backup. “The best thing is just to not irritate it,” he said before Friday’s 5-0 victory over Toronto. “Let it be for a couple days, and hopefully by the third or fourth day, I’ll be out there.” Manager Joe Girardi planned to use shortstop Alberto Gonzalez as his emergency, third-string catcher. Romine aced his first test as the temporary starter. He achieved an excellent rhythm with starter Hiroki Kuroda. He also contributed a pair of hits, including an RBI double. Romine attributed his success to a recent mechanical tweak with hitting coach Kevin Long. He added a leg kick to his swing.