The loss was the second of the three-game series against the Blue Jays -- marking the first time Oakland (41-43) had lost a series since being swept by Washington on June 7-9. The A's had won seven series in a row.
The sudden lack of control came as a surprise to manager Ken Macha. Especially since Harden entered Thursday's game with a three-game winning streak and a 0.51 ERA since returning from a strained left oblique muscle that landed him on the disabled list.
"Perhaps this is like Rich going through Spring Training and you have one of those outings when you just dont have a feel for where it's going," Macha said. "He just made one mistake. He hung a [split-finger fastball] to Wells -- a three-run homer. That's pretty much it."
Harden's sporadic performance was almost saved a batter before Wells took him deep.
With two outs in the fifth, Toronto's Frank Catalanotto sliced a pop-fly to shallow left field and Eric Brynes attempted a dive, but came up just short and Catalanotto wound up with a double.
"It was close, definately. It was a ball I should have caught," Byrnes said. "It was tough because it was one of those inbetween balls where I wasn't quite sure if I was going to have to dive for it or run through it. At the last second it just kind of dropped off the table."
A catch in that situation would have ended the inning and maintained Oakland's two-run lead -- due to a two-run homer by Byrnes in the second off Toronto starter Gustavo Chacin. Macha couldn't fault his left fielder, though.
"It's not a routine play by any means," Macha said. "Certanly that would've closed the inning off, but Byrnes gives it all he's got all the time. It really shows you the value of outs."
Wells followed with the three-run homer -- a 2-2 blast that hooked around the left-field foul pole.
"If [the pitch to Wells] was about another six inches down he would've probably been on top of it and hit it into the ground," Harden said. "But he lifted it up. He got out front a little bit and kept his hands back enough to get it up."
"Pitchers that throw that hard have a tendency to get the ball up a little bit. We laid off that and made him work," Toronto manager John Gibbons said. "He held us in check until Vern got the big hit, and it was tight the rest of the way."
Harden (5-4) left after just five innings -- his shortest outing since his first game back from the injury on June 21. He ended up with four earned runs, but it could have been less had the bullpen recorded a key out.
After walking two to start the sixth, Macha called reliever left-hander Ricardo Rincon in from the 'pen. Rincon walked Russ Adams and gave up a RBI single to the left-handed Catalanotto -- adding an earned run to Harden's total.
Rincon struggled during the Toronto series. He walked two, gave up two hits and allowed two earned runs. His two recorded outs in three appearances against the Blue Jays gave him a 27.00 ERA for the series.
"His job, basically, is to come in and get these left-handers out and he comes in and walks them," Macha said. "It makes it tough. But he has a history of pitching well so we're going to get him back on track."
After Rincon exited, Kiko Calero and Ron Flores came on and allowed no runs on no hits in the final 2 2/3 innings.
The A's only offense came from Byrne's homer, which he hit off the facing of the second deck in left field. After that shot, though, Chacin allowed just two hits to the next 16 batters he faced.
Chacin (7-5) won for the first time since June 6 and allowed just the two runs in his 5 2/3 innings for Toronto (44-41). He was 0-1 in his last five starts. The Jays' bullpen came on and finished where Chacin left off -- allowing just two hits and no runs. Toronto closer Miguel Batista pitched 1
1/3 innings for his 15th save.