With the defeat, the Yankees' American League East lead over the idle Orioles dipped to just one game with six contests remaining on the schedule.
New York's magic number to clinch the division remains at six, while their magic number to secure a postseason berth is now three. Nick Swisher said the Yankees are ready for the challenge.
"We know what's at stake right now," Swisher said. "We've just got to go out there and keep picking up wins. That's what it boils down to. We haven't played extremely well in this ballpark this year. We need to pick it up, because we've got somebody right on our tails."
Morrow has a history of pitching well against the Yankees in Toronto and was in command of New York's lineup again on Thursday, limiting the Yankees to just four hits and three walks over seven innings.
"It seems like he always figures it out against us, no matter how he's pitching or how well we're swinging or not swinging," Alex Rodriguez said. "It seems like he always figures out a way to do a good job against us."
Morrow's dominance, Rodriguez said, made this loss easier to take than the one on Tuesday in Minnesota, when the Yankees "had a stranglehold" on a game against the Twins before losing it late.
"We just stayed with a good mix of everything all night and tried to keep them off balance and not fall into any patterns," Morrow said.
Here north of the border, the Yankees weren't going to win without producing any offense. But Girardi had said that Thursday represented "an important start" for Nova, who won 16 games last year but now finds himself on the bubble for a postseason roster spot.
"I think I'm working on everything possible to pitch good, to throw strikes, to get people out," Nova said. "Unfortunately, this year has been really bad for me, but I'm not quitting. I've got to keep fighting."
Though Girardi wouldn't tip his hand on Thursday, the Yankees already have four capable starters lined up for the playoffs in CC Sabathia, Andy Pettitte, Hiroki Kuroda and Phil Hughes, making it likely that Nova would be asked to help the Yankees in relief.
Nova could also find himself relegated to a taxi squad, working out in Tampa, Fla. Girardi offered a non-committal endorsement of Nova making his final start of the year, saying, "I'll worry about tomorrow. That's five days away."
"I'm not thinking about that," Nova said. "I'm going to keep working like I'm going to start next time. If he [doesn't] give me next time, what can I do? I'm confident, I'll still work and hopefully I can get the next one and then be in the playoff rotation."
On this night, Nova was crushed for his mistakes, as the last-place Blue Jays took advantage. He issued a one-out walk to Anthony Gose in the third inning and paid as Brett Lawrie launched his 10th home run of the season, a two-run shot to right field.
"I don't think it was a strike," Girardi said. "He just left a fastball up, and Lawrie jumped all over it. I think it was above the zone, but he got to it, got the barrel to it, and got it out."
The Blue Jays added more against Nova in the fifth. Gose lined a leadoff single and Colby Rasmus dropped a beautiful one-out bunt for a hit. Edwin Encarnacion cashed in both runs, ripping a double -- the 87th extra-base hit permitted this season by Nova, establishing a new franchise record.
"Especially right now, the position that we're in, I don't feel good about it," Nova said. "We want to win every day, and I'm not doing that."
Derek Lowe allowed a run in the seventh, and David Aardsma came on for the eighth, allowing a solo homer to J.P. Arencibia as he made his Yankees debut and first big league appearance since 2010.
But the decision seemed in little question by that point. Catcher Russell Martin explained that he has seen Nova's slider betraying him of late, but the catcher believes Nova still has weapons in his corner, including an improving curveball.
"I'm not really worried about him, seeing that curveball," Martin said. "The only thing you have to eliminate right there is making mistakes with his slider. For me, I think if he just tries not to throw the slider for a strike, he'll be better off. That's it. It's a simple adjustment."
Now, Girardi and the Yankees must decide if they can afford to have Nova test that theory at the big league level. Girardi's lukewarm response to considering Nova for the playoff roster seemed to speak volumes.
"I don't know. I can't think about that," Girardi said. "I wish I could worry about that now, but I can't. I've got to worry about tomorrow's game, and then we'll go from there."