Granderson worked out in left field Thursday and the speedy Gardner switched to center. Thursday morning, Girardi told Granderson to start working in left field and informed Gardner that he should spend some time practicing in center. For the beginning of training camp at least, Granderson, who has been the every-day center fielder since arriving in the Bronx from Detroit before the 2010 season, and Gardner, who started out as a center fielder but was moved to left when Granderson arrived, will trade positions as the Yankees, having lost nearly 100 home runs through roster changes, seek ways to save runs on defense. Granderson said he accepted the decision but made his preference clear. "If we went out there and played right now, I'd go to center, I'd go to left, it doesn't really matter to me.'' You never know unless you try things out. Asked who would be his center fielder when the Yankees travel to Kissimmee to play the Braves in their first spring game on Saturday afternoon, Girardi deadpanned, "Melky Mesa." The Yankees lost plenty of firepower on offense since last year, so their ability to prevent runs will be of greater importance this season.