Boston's Clay Buchholz bounced back from a blow to the head, but couldn't overcome his lack of control.
Jose Bautista homered and drove in two runs, R.A. Dickey won for the first time in three starts and the Toronto Blue Jays beat Buchholz and the Red Sox 6-4 on Wednesday night.
Buchholz (5-6) was knocked to the ground in the first inning when a comebacker from Munenori Kawasaki bounced over his glove and struck him on the right temple.
"It dazed me for sure," Buchholz said. "Anytime you get hit with a ball it's going to take you a second."
After being checked by manager John Farrell and the trainer, Buchholz took a few warm up pitches, and declared himself fit to continue.
"I feel fine," he said afterward. "It might be a little sore tomorrow but I'll be all right."
Buchholz lost for the first time in three starts, allowing five runs, four earned, and six hits in six innings. He walked four and struck out one.
"The overall sharpness wasn't what it's been the last four times out," Red Sox manager John Farrell said of Buchholz, who had walked just one in his previous five outings.
David Ortiz hit a three-run homer for the Red Sox, his fourth in three games, but Boston lost its second straight after winning five in a row.
Staked to a 3-0 lead before he threw his first pitch, Buchholz couldn't make it stand up for long. Jose Reyes singled and Melky Cabrera walked to begin the bottom of the first before Bautista hit an RBI double. Bautista scored on a grounder and Josh Thole hit an RBI double over the head of Daniel Nava in left.
Boston started even faster against Dickey in the top of the first. After Shane Victorino and Dustin Pedroia singled, Ortiz clubbed a towering drive off the facing of the fourth deck. The homer was his 455th, tying him with Adam Dunn of the Chicago White Sox for 35th on the career list.
Ortiz's drive was his 37th at Rogers Centre, breaking a tie with Alex Rodriguez for the most by a visiting player.
Ortiz, who went deep in consecutive at-bats Monday and connected again Tuesday, homered in three straight games for the first time since June 17-20, 2012.
The three RBIs gave Ortiz 1,501 for his career, making him the 53rd player in major league history with 1,500 or more.
Boston reclaimed the lead with consecutive doubles by Nava and Xander Bogaerts in the fifth, but Toronto answered with two runs off Buchholz in the sixth. Thole walked and scored on Ryan Goins' first career triple. Two batters later, Goins scored on a throwing error by third baseman Bogaerts.
"It seemed like he didn't quite get his feet set to deliver a firm throw," Farrell said.
"I let that lead go," Buchholz said. "I'll take the blame for this one, for sure."
Bautista made it 6-4 with a first-pitch homer off Andrew Miller in the seventh that bounced off the top of the wall and out. The drive was his first since July 2.
Dickey (8-10) allowed four runs and nine hits in six innings, walked one and struck out five.
"That knuckleball is so unpredictable," Boston's Mike Napoli said. "We had it going early then he kind of shut us down."
Rookie Aaron Sanchez, selected from Triple-A Buffalo on Tuesday, made his debut with two scoreless innings.
"Pretty impressive," Blue Jays manager John Gibbons said. "I don't know how you can do it any better than that."
Sanchez, whose parents flew in from California to watch his debut, was all smiles afterward.
"It's been a whirlwind these last 48 hours," he said. "To have my start like that is pretty awesome."
Casey Janssen finished for his 15th save in 17 chances.