Boston has mustered a total of six runs over the last four games to fall 12 games back in the American League East.
"Early in the season, we were hitting a lot of hard-hit balls at guys. Now, I don't know. We're giving everything we have and trying to win ballgames, but it's just going that way for us right now," said third baseman Xander Bogaerts.
In the bottom of the ninth, Bogaerts provided one of the few hitting highlights of the night for Boston, belting a solo homer against Jays closer Casey Janssen.
Rubby De La Rosa suffered his first loss in five starts this season at Fenway Park, but put together a solid enough effort. The righty gave up nine hits but just three runs over six innings.
"I thought Rubby gave us an opportunity to win," said manager John Farrell. "He pitched with some men on base. With the exception of the 3-1 changeup to [Anthony] Gose that doesn't get to the spot for the two-run double on his part, I thought he gave us a solid, solid effort, and we had probably three opportunities where we had multiple men on base, and the timely hit was elusive."
Following the game, speculation about Lester's possible exit became more rampant, when Farrell announced the lefty was scratched from Wednesday's start. Brandon Workman will come up from the Minors and take that turn in the rotation.
"Yeah, Brandon Workman will start [Wednesday]," said Farrell. "In light of all the uncertainty surrounding Jon Lester, it's probably in everyone's best interests that he does not make that start, so Brandon will be recalled. There will be a corresponding move roster-wise at some point tomorrow."
Dustin Pedroia, who doubled home a run to tie the game in the bottom of the third, doesn't think the Lester situation has led to the team's latest slump.
"We've got a lot of guys around here who are pretty good at putting the distractions aside, but we just haven't found a way to win games," Pedroia said. "That's basically it."
The Jays took the lead on a solo homer to center by Colby Rasmus in the top of the second.
After Pedroia tied it with his smash off the wall, De La Rosa couldn't keep momentum on Boston's side in the top of the fourth.
Juan Francisco led off with a single. Rasmus drilled a single up the middle to put runners on first and second with nobody out. With two outs, Gose smoked a two-run double into the corner in right to make it 3-1.
For the second time in less than a week, Marcus Stroman (seven innings, one run) stifled the Red Sox.
"He's on some kind of roll right now, but the kid is good," said Jays manager John Gibbons. "He believes in himself, he has all the confidence in the world, and he has the stuff for it, too. It's not easy, facing the same team twice in a week. In 14 innings, he has given up one run to them -- that's hard to do. I tip my hat to the guy. He's pitched a lot better than I thought he was going to if you want to know the truth."
With one game left before the Deadline, the Red Sox can only wonder who will be in their clubhouse on Friday, when they open a three-game series against the Yankees.
"That's what always happens at this time of the year," said Sox slugger David Ortiz. "It's very uncomfortable until the Deadline day. The Deadline, it's a situation where everybody doesn't get too comfortable. We've got a couple days still. We'll see."