Menechino came off the bench to drive in three runs, Eric Hinske hit a go-ahead double and Toronto rallied past New York 8-6 on Sunday.
Shea Hillenbrand had four hits and Corey Koskie homered for the plucky Blue Jays (14-12), aggressive on the bases all weekend. They have won five of six following a five-game skid.
"They don't quit. If I don't get in the way we might have a good year," Toronto manager John Gibbons said.
Gary Sheffield homered and drove in three runs for the slumping Yankees (10-15), who blew a 6-3 lead and finished 3-6 on their homestand -- losing series to the Rangers, Angels and Blue Jays.
New York dropped 7½ games behind AL East-leading Baltimore, its largest deficit since September 1997.
"The Baltimore Orioles are not what I'm concerned about. What I'm concerned about is our ballclub. We've had leads in the past that have disappeared when teams got hot. We have to be that team that gets hot," Yankees manager Joe Torre said.
"I don't care how good you are or how good you're supposed to be. You have to go out there and start winning regularly or your confidence isn't where you want it to be," he said. "I don't think I have to tell them anything. They're here. They witnessed what I witnessed."
With the score tied at six, Hillenbrand and Hinske hit consecutive doubles off Mike Stanton (0-1) in the seventh to give Toronto the lead.
Hinske stole third and dashed home on Gregg Zaun's shallow sacrifice fly to center, making it 8-6.
"I had Hinske 0-2 and I let him beat me. There's no excuse," Stanton said. "Coming into the season, everyone thought the bullpen would be a strength for us. It hasn't turned out to be that way. Track record says it's going to get better."
Hinske's two-run homer off Randy Johnson that sent Roy Halladay and the Blue Jays to a 2-0 victory Friday night.
"It's great because we came in here, and the New York media not once talked about what we were doing. It was just, what's wrong with the Yankees? We don't care about the Yankees," Hillenbrand said.
In a matchup of 2004 All-Stars, New York starter Carl Pavano and ex-Yankee Ted Lilly were both ineffective.
Pete Walker (1-0) pitched 1 2/3 hitless innings for the win. Scott Schoeneweis retired Jorge Posada with two on to end the seventh, then worked a perfect eighth. Miguel Batista got three straight outs for his seventh save in eight chances.
"We showed what we're made of," Schoeneweis said.
Sheffield put the Yankees ahead with a two-run double during a four-run fifth. Posada added a sacrifice fly and Hideki Matsui an RBI double to make it 6-3, but Toronto executed a fine relay to throw out Alex Rodriguez at the plate and end the inning.
It didn't take the Blue Jays long to pull even. They loaded the bases with none out in the sixth, chasing Pavano. Alex Rios hit a sacrifice fly, and Menechino tied it with a two-out, two-run single on a 1-2 pitch from Paul Quantrill.
Menechino entered in the fourth inning to replace second baseman Orlando Hudson, shaken up after colliding with an umpire.
"I think my first at-bat got me locked in," Menechino said. "I don't mind hitting with two strikes, I think I bear down a little bit better."
Menechino, who was raised in Staten Island and still lives there, had friends in the Yankee Stadium stands all weekend.
"They're all Yankee fans anyway," he said. "I give them tickets so they can see Randy Johnson pitch."
Rodriguez doubled in the second and scored on Matsui's sacrifice fly for a 1-0 New York lead.
Rios doubled leading off the third and scored on Hudson's RBI groundout. Koskie's fifth home run gave Toronto a 2-1 edge in the fourth.
Sheffield connected on an 0-2 pitch in the bottom half, becoming the first Yankees player other than Rodriguez to homer since Derek Jeter and Andy Phillips on April 24.
The Blue Jays went ahead 3-2 in the fifth after Sheffield failed to come up with Frank Catalanotto's deep fly to right, a catchable ball that went for a double and put runners at second and third. Menechino followed with an RBI groundout.