Dalesandro, pinch hitting for Felipe Crespo, hit a high chopper to shortstop Miguel Tejada, with Jose Canseco beating the throw to the plate.
"Being a role guy you have to be mentally ready when you come in the game like that," Dalesandro said. "I've been in this role my whole career at the major league level, so I think that now that I'm older I'm able to handle it better and understand when I might be used."
With one out, Mike Fetters (1-6) walked Canseco, Carlos Delgado doubled to left, and Jose Cruz Jr. was intentionally walked to load the bases before Dalesandro singled.
"I jammed him, he didn't hit hard, he topped it and hit it off the plate and he was just luckier than I was today," Fetters said.
Dan Plesac (4-3) pitched the 10th for the victory.
Toronto, which snapped a three-game losing streak, tied it at 5 in the eighth after Tejada botched a ground ball for an error allowing Shawn Green to reach. One out later Delgado hit an RBI double off Buddy Groom.
"One unearned run did us in today," Oakland manager Art Howe said.
Oakland scored two runs in the fifth to take a 5-4 lead. Pat Hentgen loaded the bases on a single and two walks, then hit Matt Stairs with a pitch to tie it at 4. Jason Giambi followed with a sacrifice fly to give the Athletics the lead.
Shawn Green put the Blue Jays up 2-0 in the first with his 21st homer.
Oakland cut it 2-1 in the second. Former Blue Jays third baseman Ed Sprague hit an infield single and scored on an error after Tejada's double to right. Sprague initially held at third, but scored after the throw back into the infield ticked off Delgado's glove.
Ben Grieve hit a two-run homer, his 15th of the season, to give the A's a 3-2 lead in the third.
Toronto took a 4-3 lead in the fourth. Canseco hit his 32nd homer, and Tony Fernandez had an RBI single.
Hentgen, winless at home since May 20, gave up five runs on five hits and four walks in five innings. Oakland starter Blake Stein, scratched from his scheduled start Friday night because of a tender right shoulder, gave up four runs and seven hits in four innings.
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