"How many did they end up with?" Jeter asked afterward. "I don't even know."
New York's previous worst loss was a 12-2 home loss to Baltimore on May 20.
A playoff team every year since 1995, the Yankees know their chance to extend that streak is in serious doubt.
"It's up to us," Jeter said. "We have to start stringing together some wins. We can't just keep winning one here, losing one there. We've got to get on a streak here. Hopefully that can start [Friday] night."
The Yankees opened the second half with an eight-game winning streak but have won just one of seven series since, dropping four and splitting two.
"That's not good enough," manager Joe Girardi said. "We have to do better if we want to play in October."
Outfielder Johnny Damon said the unbeatable feeling the Yankees had during their post-All-Star run has vanished.
"It seemed like things were going our way," Damon said. "We made things happen, we had that winning attitude. Right now it feels like we have to be a little perfect. We have to do everything right to catch a break and get a win."
Halladay (15-9) improved to 13-5 in 30 career games against the Yankees, allowing three runs and five hits in seven innings. He walked two and matched a season high with nine strikeouts.
"He's not the best pitcher in the game for nothing," Damon said. "He's not going to leave the ball in the middle of the plate, he's not going to throw too many straight pitches. He's so good. He'd be the ace on any team in the big leagues."
Joe Inglett had a career-high four hits, Scutaro matched career highs with four hits and four RBIs as Toronto had 21 hits, one shy of a club high this season.
Sidney Ponson (7-4) matched a season high by allowing seven runs and eight hits in two-plus innings. He walked one and didn't strike out a batter.
"I didn't have anything," Ponson said. "My sinker wasn't there, my slider wasn't there, my change-up wasn't there. I pitched like crap and I let these guys down today."
The right-hander has won twice in 10 starts since New York signed him June 19.
"Sidney couldn't find his rhythm and we had to go to the bullpen early. They just kept tacking on," Girardi said.
Rios singled home a run in the first and Rod Barajas' second-inning sacrifice fly made it 2-0 before Toronto broke it open with a five-run third, sending 10 men to the plate.
Inglett and Scutaro began the inning with back-to-back singles and scored on Rios' double before Vernon Wells walked. Lind chased Ponson with an RBI single. After walking Lyle Overbay, Robertson got two outs, then gave up a two-run, broken-bat single to John McDonald.
The Blue Jays added three more in the fourth on a bases-loaded double by Stairs before Scutaro drilled a three-run drive to left in the fifth, his fifth.
Toronto finally came up empty in the sixth, when Edwar Ramirez came on to strike out Scutaro, leaving the bases loaded.
Blanked by Halladay through the first six innings, New York got on the board in the seventh when Hideki Matsui hit a three-run homer to right, his eighth, giving him 499 career RBIs. Matsui, who returned Tuesday after missing 49 games due to a sore left knee, homered for the first time since June 12 at Oakland.
Scutaro capped the scoring with an RBI double in the eighth against right-hander Chris Britton.
Wells, who finished 0-for-4 with a walk, was the only Toronto starter not to get a hit.
Yankees RHP Carl Pavano will start in Baltimore on Saturday, his first start since ligament replacement surgery last season. ... New York RHP Joba Chamberlain (rotator cuff tendinitis) threw 20 fastballs on flat ground Thursday. He'll take Friday off and throw 30-35 fastballs and changeups in a bullpen session Saturday. ... Toronto acquired INF/OF Jose Bautista from Pittsburgh for a player to be named and will open a roster spot when he joins the team Friday. ... Two Toronto minor leaguers, 2B Scott Campbell and DH Travis Snider, were selected to the Double-A Eastern League All-Star team.