There is nothing foolish about Derek Jeter’s re-entry into the Yankees’ universe, but the only date that matters to him is April Fools’ Day. Jeter, who has yet to play in an exhibition game, wants the left ankle he fractured last October to be ready by April 1 when the Yankees open the season against the Red Sox at Yankee Stadium. “I am always eager to play, but keep in mind April 1 and that hasn’t changed,’’ Jeter said following yesterday’s workout at George M. Steinbrenner Field. “Trust me, I will play when I get the OK to do so.’’ General manager Brian Cashman recently said March 10 was a loosely defined target date for Jeter to play in exhibition games. While that would be nice, it’s not set in concrete. “I’ve got to run bases, I have run them but I have to run them harder,’’ Jeter said. “It’s like any progression when you get hurt. When I hurt my calf it was the same thing when I came back. It was running in a straight line, running the bases and running the bases hard. I don’t necessarily think it’s a check list.’’ As for the March 10 return date, Jeter was wide open. “Why not? But I don’t put dates on it,’’ Jeter said. “That was a date that was floated out there. I will play as soon as I can, before or after.’’ Manager Joe Girardi is waiting on Jeter before deciding what his lineup will look like and where he will put Brett Gardner and Ichiro Suzuki.