McCoy, the seventh Toronto pitcher, retired Boston's Carl Crawford, Marco Scutaro and J.D. Drew in order to record a perfect frame.
The 30-year-old is the fifth position player to pitch for the Blue Jays in their franchise history. The last was Frank Menechino on Aug. 28, 2004.
"Earlier in the year, there was a blowout game and I said, 'If you need me to pitch, I can,'" McCoy said of his conversation with manager John Farrell. "Save the bullpen a little bit, one inning, so he knew I could do it."
McCoy threw mostly slow changeups from 60-76 mph, but mixed in a couple of sliders and topped out with an 85-mph fastball.
He said the goal was to throw the ball slow enough that Boston's hitters would have a tough time making the adjustment.
"Throwing softer is usually more effective," said McCoy, who added he once threw 3 2/3 innings in a Minor League game in 2009 after his team ran out of pitchers. "Big league hitters are used to seeing 90 mph and I'm throwing 72-73; they usually get themselves out on that."
The variance in speed proved to be effective. Crawford hit a weak fly ball to shortstop, Scutaro flew out to left and Drew hit a soft ground ball to second base.
Crawford couldn't help but laugh at the situation when the game was over.
"You don't know what's going to happen," Crawford said. "The main thing is you just try to get a hit. Hope not to strike out or something like that. You don't want to get out. It's a very different situation."
Crawford added he didn't have any idea what pitches McCoy was throwing.
"Knuckleball, knuckle change or something," Crawford said. "I don't know what it was. He sure made it look easy, I'll tell you that."
McCoy has played seven different positions during his three-year career in the Majors. The only spots he has not played are catcher and first base.
The native of California left the game to a standing ovation from the crowd at Rogers Centre. He said it was a moment he won't soon forget, but that doesn't take any of the sting away from a disappointing loss.
"It was pretty exciting for me, but it's a loss and we need to come back tomorrow and give it my best shot," McCoy said.