With Rivera unavailable on Saturday as he continues to guard a mild injury, Hughes stepped up to record a four-out save and preserve the victory for Pettitte and the Yankees, who dispatched the Blue Jays with a 6-4 decision at Rogers Centre.
The victory was the Yankees' ninth in 11 games and their 59th in 60 contests when they lead after six innings, a tribute to their bullpen's bridge leading into the final frame, normally occupied by the future Hall of Fame closer.
"It's not very often you get to save games on the Yankees, if your name isn't Mariano," Hughes said. "It's been nice, and I think we have the depth and arms in the bullpen to pick up the slack, if he needs a break."
Robinson Cano and Mark Teixeira slugged solo homers to back Pettitte on an afternoon that the left-hander called "a struggle all day," quite the contrast when played up against his last start against the Orioles in Baltimore.
In that performance, Pettitte had the news agencies on red alert as he cruised almost effortlessly into the seventh inning, making a serious bid for what would have been his first perfect game or no-hitter at any level of organized baseball.
With the roof open in Toronto on a beautiful day, Pettitte wasn't exactly as dominant, but his changeup was serviceable enough to leave after six innings without wanting to to issue himself too harsh of a tongue-lashing.
"I wasn't locating my fastball to either side of the plate, and I had trouble getting my breaking ball over," Pettitte said. "I was real fortunate."
Pettitte's advantage came courtesy of Teixeira, whose fifth-inning shot -- his team-leading 33rd -- off Toronto left-hander Brett Cecil put New York ahead to stay, matching Teixeira's 2008 season total.
Melky Cabrera got the Yankees started against Cecil in the second inning with an RBI single, and Cano added a solo homer in the fourth, his 23rd, that was caught by bullpen coach Mike Harkey in the right-field bullpen.
Alex Rodriguez and Jorge Posada added RBI singles to give the Yankees their fourth and fifth runs, as Pettitte completed six innings, allowing four hits and four earned runs.
Pettitte walked five and struck out three in winning his fourth consecutive start and remaining undefeated in his eight starts since July 30. The Yankees are 20-8 when Pettitte starts this season, their best mark under any member of their pitching staff.
Pettitte nearly gave up a solo home run to Toronto designated hitter Randy Ruiz in the second inning, a rocketed shot that slammed in close proximity to the left-field foul pole.
But Jerry Hairston Jr. and Derek Jeter alertly noted that the ball shot back to the field unlike one that would hit the mesh netting, and after a review, crew chief Tim Tschida agreed and overturned the homer.
"I thought it was a homer, but immediately Jeet and the guys came over and said it shot off," Pettitte said. "I didn't even pay attention to how hard it was hit, but they said, 'Dude, it shot off like it hit the concrete up there.' Then I realized, maybe it did hit the concrete."
Pettitte's luck wouldn't last forever; in Ruiz's next at-bat, he did belt his sixth homer of the year, a no-doubt line drive into the left-center-field seats.
Toronto tied the game later that inning on a John McDonald RBI single that fell into right field between Eric Hinske and Cano, but Jose Bautista was thrown out representing the go-ahead run by Cano, who had alertly chased the bloop hit into right field and fired home to Posada.
"His presence of mind not to quit on the play was really important," manager Joe Girardi said.
The Blue Jays got as close as 5-4 against Pettitte, who labored to 101 pitches (60 strikes). With one out and one on in the sixth, Bautista tripled to deep center, the drive landing safely as Cabrera fell backwards into the wall.
As Edwin Encarnacion scored, Jeter's throw went to third base and skipped away, allowing Bautista to come home. With Rivera out due to a tight left groin, but scheduled to be available on Sunday, watched approvingly, the Yankees' relief corps held it there.
"We're very fortunate," Girardi said. "We've got guys who can throw the ball extremely well. All the guys down there have done that for us. It changes your rotation a little bit, but the guys have stepped up in Mo's absence."
Dave Robertson hurled a scoreless seventh and Brian Bruney recorded two outs in the eighth before Hughes was summoned in relief for his second four-out save chance of the week, retiring all four Blue Jays he faced while using his cutter, fastball and curveball judiciously.
"Phil's done a great job," said Jeter, who had two hits and needs six more to tie Lou Gehrig's club record of 2,721. "Setting up for Mo, he's done a great job, and today it didn't seem like he was fazed by anything. He's coming after guys and throwing strikes."
On Wednesday, Hughes inherited a 3-2 lead and watched the Yankees blast a seven-run ninth to make it a laugher.
He wasn't given quite so much slack on Saturday, though Cabrera's second RBI single of the day brought home Cano in the ninth to give the Yankees an insurance run that Hughes greatly appreciated.
"I think I have the confidence now to pitch within the strike zone and not necessarily nibble all the time," Hughes said. "That's something I had in the Minor Leagues because I trusted my stuff. I think I trust my stuff that much again."
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.