"It's just another loss. I don't think it's any tougher than any other loss," first baseman Adrian Gonzalez said. "We've got to find a way in the next series to play better baseball."
Just 3-10 in September, the Red Sox maintained a four-game lead in the AL wild-card race over Tampa Bay, which lost its second straight in Baltimore. Boston led the AL East at the start of the month and was nine games ahead of the third-place Rays.
After getting swept in a three-game series at Tampa Bay last weekend, Boston hosts the Rays in a four-game series starting Thursday night.
"Very frustrating," said Bard, 0-3 with a 30.86 ERA in his last three appearances. "I've been through it before. "Sometimes the effects are magnified by how big the games are."
Loewen, converted to outfielder from pitcher, was 0-1 with a 6.63 ERA in four starts against the Red Sox for Baltimore in 2006 and '07.
"I'm very aware of that. They got me," he said, dressed in a ballerina costume as spoke to the media, part of late-season rookie hazing. "I think the best chance I had was against (Josh) Beckett in our place. I came out of the game (ahead) 2-1 in the sixth, and they ended up winning it in the top of the ninth."
Loewen has taken advantage for openings created by injuries.
"September is about taking a look at all of our personnel and he's capitalized on every opportunity, so there's no reason to think that's not going to still be in the rotation and in the mix," Toronto manager John Farrell said.
Ricky Romero (15-10) allowed four runs -- three earned -- and six hits in eight innings. He improved to 8-1 in his last 10 starts.
Frank Francisco pitched a 1-2-3 ninth for his 15th save in 19 chances as the Blue Jays won for just the third time in nine games at Fenway Park this season.
Red Sox starter John Lackey gave up two runs and seven hits in 5 1/3 innings. He threw 115 pitches.
"He had a high pitch count, mainly early," Boston manager Terry Francona said. "When he came out of the game, we had a good chance to win."
Toronto took a 2-0 lead in the first on consecutive run-scoring singles by Encarnacion and Johnson, but Boston tied it in the second when Ryan Lavarnway reached on a run-scoring error by third baseman Brett Lawrie and an RBI grounder by Jason Varitek.
In the sixth, Varitek held on and tagged out Lawrie, who came crashing in with his forearms while trying to score from third on Adam Loewen's bouncer to second with the infield in, Varitek flipped over backward.
Gonzalez left with left calf tightness after his homer. He said it tightened up in his previous at-bat and bothered him on his home-run trot. "When I was rounding the bases, it got worse as I kept going," he said before saying he hoped to play Thursday. ... Lawrie left with a bruised knee. ... Red Sox DH David Ortiz missed his second straight game with muscle spasms in his back. "He really wanted to play today," Francona said. "He woke up this morning and was real sore, but he's moving around better." ... The Red Sox honored RHP Tim Wakefield with a brief on-field ceremony after he became the 108th player in major league history with 200 career wins in Tuesday's 18-6 victory over the Blue Jays. ... Francona was also honored on the field for being elected to the National College Baseball Hall of Fame earlier this year. ... Toronto SS Yunel Escobar missed both games in Boston because of a bruised left arm. ... The Blue Jays have a day off Thursday before they attempt to stop the Yankees' CC Sabathia (19-8) from winning his 20th game. Brett Cecil (4-9) is scheduled to pitch for Toronto. ... Kyle Weiland (0-1) opens the series against the Rays' Jeremy Hellickson (12-10) on Thursday.