"It's definitely a heartbreaker," Jays skipper John Gibbons said. "We've seen it too many times in this place."
The Rays picked up their ninth walk-off win of the year with three coming against the Jays this season. Upton has two walk-off RBIs in his career, both coming this year and both against the Jays, including the Opening Day RBI single at Tropicana Field.
"We just allowed extra outs at the end and walks," said Gibbons. "They have guys who can take you deep and that's what happened."
Accardo started the ninth with a 4-1 lead after Jays starter A.J. Burnett had tossed eight impressive innings. Carl Crawford reached on an error by shortstop John McDonald to start the inning.
"It was to my right and I went to glove it and throw it on the run and I just didn't catch it," said McDonald. "It's not an abnormal play. I was in position to make the throw and I just didn't do it."
Crawford advanced to second uncontested during Carlos Pena's at-bat and then advanced to third on a groundout to first by Pena.
Rays rookie Delmon Young then smacked Accardo's first pitch offering the opposite way, barely clearing the right-field wall to reduce the Jays' lead.
Following a walk to Jonny Gomes, Jays pitching coach Brad Arnsberg visited Accardo on the mound.
"We just told him to settle down and he knew what he had to do," said Gibbons.
But then, Upton, who did not start the game because of a bruise to his left ankle, came to the plate as a pinch-hitter and promptly ended the game on the first pitch he saw from Accardo.
"It's just terrible the way things went down," said Accardo, who suffered his fifth blown save of the season. "I got beat to [the opposite low side] twice. I can't pitch to the opposite side of the plate the whole side, especially to Young and Upton, who are strong guys. I just got beat."
The loss spoiled another solid outing from Burnett, who appeared to be headed for his fourth win in six games since returning from the disabled list.
Burnett, who has a 1.92 ERA over his past six starts, scattered three hits, and after allowing a solo home run to Dionner Navarro in the second inning, retired 10 batters in a row and 18 of the last 20 batters he faced.
"He was really impressive, once again," Gibbons said. "Early on, he was just throwing, but then he started throwing more breaking stuff, more curves and he shut them down for eight innings."
While Tampa Bay had difficulties figuring out Burnett, Toronto finally figured out how to get to Rays starter Jason Hammel, who had shut down the Jays for five innings until Alex Rios gave Toronto a 2-1 lead in the sixth with a two-run shot for his 23rd homer of the season. The Jays added two more in the seventh off reliever Grant Balfour and appeared to be on their way to a third consecutive win.
With 21 games left in the season, the Jays (72-69) -- now 7 1/2 games behind the Yankees in the Wild Card race -- must hope New York, Seattle and Detroit falter down the stretch. After finishing the series with the Devil Rays in St. Petersburg on Sunday, the Jays travel to Detroit for a make-up game. The Jays do not face the Mariners anymore but still have seven games left with the Yankees, including a three-game home series that begins on Tuesday and then a four-game set that begins 10 days later in New York on Sept. 21.