"The Red Sox can only hope Jon Lester is as good at self-diagnosis as he is at pitching.

The ace lefty seemed unfazed by the strained lower latissimus dorsi muscle in his back that forced him to leave last night's 3-2 win over the Toronto Blue Jays after four no-hit innings.

There was plenty of concern when Lester left after throwing 50 pitches, allowing only a walk. He felt cramp-like pain in the large, triangular muscle that covers the lower back during the fourth inning. He consulted with trainer Mike Reinold and was removed from the game.

Lester will undergo an extensive evaluation today, but his initial reaction was that the injury was minor.

"We may alter one start, but we've got the All-Star break built in," Lester said. "I don't imagine this being a long-term deal. We'll re-evaluate everything (today). Hopefully, this was just a more precautionary type (of) deal, just a fluke thing, and move on."

Lester left with a 3-0 lead, and relievers Matt Albers, Franklin Morales and Daniel Bard combined for four scoreless innings. Albers (3-3) pitched two shutout innings to earn the win.

The Sox had to hold on in the ninth, as Jonathan Papelbon [stats] allowed a two-run homer to Jose Bautista and had runners on first and second with two outs when John McDonald singled to left. A charging Darnell McDonald fired home to nab Edwin Encarnacion as Jason Varitek [stats] blocked the plate."