Boston's Jon Lester delivers a pitch in Tuesday's 1-0 triumph over Toronto. (Charles Krupa/Associated Press)

Another complete game, another heartbreaking loss for Roy Halladay and the Toronto Blue Jays.

Halladay suffered his third loss in four starts — all complete games — as the Blue Jays were edged 1-0 to the Boston Red Sox at Fenway Park on Tuesday night.

"It is a tough way to lose," he said. "You never get used to it."

Kevin Youkilis won it with a run-scoring single in the bottom of the ninth inning off Halladay (2-4), who retired the first two batters before issuing a walk to David Ortiz and yielding a looping single to Manny Ramirez.

"Ortiz and Ramirez, they can beat you with one pitch," Halladay said. "You want to be aggressive."

Youkilis lined a single up the middle to score a slow-moving Ortiz from second base with ease because Blue Jays centre-fielder Vernon Wells dropped the ball.

"He didn't have a chance," Youkilis said of Wells trying to throw out Ortiz at home plate.

"Even though Papi is probably not running that well right now, he put it into second gear."

"I said, 'Go ahead and send him,'" Red Sox manager Terry Francona said. "The way Halladay was pitching, take your chance with one because that might be all we had."

Youkilis finished two-for-four with a stolen base as the Red Sox (16-12) halted a five-game losing skid.

Jonathan Papelbon (1-0) posted the win in relief of Boston starter Jon Lester, who allowed just one hit and four walks with six strikeouts in eight scoreless innings.

"Any time you go up against a pitcher like Halladay, you know it is going to be a long night," Lester said. "It seems like, the further I get into games, the more comfortable I feel with my stuff and what we're trying to do."

Halladay scattered five hits over 8 2/3 innings with one walk and five strikeouts, permitting just one fly ball through seven.

"Great pitching on both sides is what it came down to," Blue Jays manager John Gibbons said.

Scott Rolen doubled and Lyle Overbay had the other hit for the Blue Jays (11-16), losers in 10 of their last 13 outings.

With files from the Canadian Press