Pettitte was to have started the Yankees' second game of the year on April 2 against the Toronto Blue Jays but back spasms have led the team to schedule Mike Mussina as the New York starter for that game.

Pettitte is expected to make his 2008 debut April 3 or 4.

He reported the back injury after driving from the Yankees' spring training facility last week. He threw 47 times Monday and was scheduled for treatment Tuesday and another throwing session Wednesday.

Pettitte was 15-9 last season with a 4.05 earned run average. He was also among the players named in the Mitchell Report on use of performance-enhancing substances in baseball.