Before the game, Red Sox manager Bobby Valentine was confident that Beckett could avoid his first-inning woes. But that didn't happen.
Beckett began the night by striking out Anthony Gose. After that, things took a turn for the worse.
Colby Rasmus lined a triple off the wall in right field. He then scored on a close play at home on Edwin Encarnacion's grounder to third baseman Will Middlebrooks, avoiding the tag from catcher Kelly Shoppach and just getting a finger on the plate.
"Off the bat I knew I had a shot at him at home," said Middlebrooks, who scored Boston's only run in the ninth inning. "I thought Kelly blocked the plate pretty well, but it was hard for me to tell. He didn't have a real big lead off of third, I was playing about halfway in so I knew I had a shot at home and took it. I was trying to save the run for Josh."
Valentine argued the call to no avail.
"He was out pretty easily," Valentine said. "It wasn't like a bang-bang play."
Beckett then allowed back-to-back singles as Toronto scored again. His first-inning ERA is now an eye-popping 10.69. For the 11th time in the last 12 games at Fenway Park, Boston's starter allowed at least one run in the first inning.
Red Sox pitchers have combined for a 6.70 ERA in the first inning this season, compared to 3.80 in subsequent innings.
The Jays got to Beckett for two more runs in the second, courtesy of Rasmus' two-run double.
Beckett settled in after that, though, with his only blemish over his final four frames an unearned run in the fifth. He struck out seven in six innings, giving up five runs (four earned) on seven hits with three walks.
It was Beckett's eighth loss this season. Toronto has plagued him during his career, and it was no different on Friday night. Beckett has a 6.28 ERA against the Blue Jays, his highest mark against any American League team.
"Obviously the results aren't what you want them to be, but I have to keep going out there," Beckett said. "I can't say that I'm looking at a whole lot of positives from that outing. I got burned whenever I didn't make pitches."
One of the pitches Beckett didn't make came against Gose in the second inning. Beckett had a chance to end the frame unharmed, but he missed his location with a curveball on a full count to put two men on base for Rasmus.
"You have to make the 2-2 pitch or 3-2 pitch, and I didn't do that," Beckett said.
Rasmus sent Beckett's next offering into the gap in left-center field to stretch Toronto's lead to 4-0.
"I think he lost a little concentration and threw a fastball over the plate to Rasmus, and before we knew it, it was two runs," Valentine said. "But he's out of that inning if he gets [Gose] out."
Facing a left-handed starter for the third time in as many nights, the Red Sox couldn't figure out Aaron Laffey. Boston typically relishes the chance to go against a southpaw, with a 20-10 record against left-handed starters entering Friday's contest.
Instead, Laffey held the Red Sox scoreless over seven efficient innings, besting his six scoreless frames against them in his last outing at Fenway Park on June 26.
"He was just hitting spots, keeping the ball down," Middlebrooks said. "When you keep the ball away and keep it on the black down at the knees, it's hard to do much with it."
Laffey pounded the zone with fastballs and sinkers, throwing just three changeups and no breaking balls.
"If you have good fastball command, you just keep rolling with it," Laffey said. "If you're getting the ball put on the ground and soft balls in the air, why change what's working? That's one thing that's big for me, if a guy hasn't beat me yet on what I've been getting him out with, I'm going to keep throwing the same thing until he beats me."
The Red Sox had few scoring chances. Dustin Pedroia flied out to right with runners on first and third to end the third. In the seventh, Jacoby Ellsbury fouled out with Middlebrooks on third to end the threat.
First baseman Adrian Gonzalez was hitless in four at-bats to snap a streak of five straight games with at least two hits.
With a single in the first inning, left fielder Carl Crawford has hit safely in all five games since making his season debut on Monday.