TORONTO (Reuters) - The struggling Boston Red Sox's latest defeat was made all the more painful after ace pitcher Josh Beckett was forced to abandon the mound early in the game with a right ankle injury on Monday.

Beckett felt discomfort in the ankle during the fourth inning of a then scoreless contest against the Toronto Blue Jays and was promptly removed.

He will fly back to Boston on Tuesday to have his ankle reexamined by the team doctor.

"I felt it on the second to last pitch and then it felt a little bit different on the last pitch," Beckett told reporters.

"It's always concerning. That's my power leg."

The Red Sox went on to lose to the Blue Jays 1-0 in 11 innings to slip 2 games behind the first-place New York Yankees in the American League East.

Despite losing a fifth game in seven contests, Boston (84-56) remain commanding leaders of the AL Wild Card race, but their playoff prospects are reliant on a fit and healthy Beckett, who is 12-5 with a 2.49 ERA this season.

"Obviously he's been our best guy from day one," Boston reliever Daniel Bard said. "We need him down the stretch."

(Writing by Jahmal Corner in Los Angeles; Editing by John O'Brien)