FORT MYERS, Fla. � Josh Beckett's back went into spasm while warming up for today's spring training game. The Boston Red Sox ace left without facing a Florida Marlins batter.

Beckett seemed to lose his footing on his last warmup pitch and called catcher Jason Varitek to the mound. Beckett put his right hand on the lower middle part of his back and soon was joined by manager Terry Francona and teammates. The right-hander walked to the dugout without an apparent limp.

Beckett was the only 20-game winner in the majors last season.

Manny Delcarmen replaced him on the mound.