Updated

The biggest reason for the Oakland Athletics' perfect record this season when leading after eight innings is their stingy relievers.

On a day when the normally reliable bullpen failed, Cliff Pennington bailed the team out.

After failing to get a sacrifice down, Pennington managed to win the game with an RBI single in the bottom of the ninth inning that gave the A's a 5-4 victory over the Toronto Blue Jays on Wednesday.

"Our bullpen has been the strength of our team all year," Pennington said. "For the offense to pick them up one time is nice."

The A's blew a 4-1 lead in the top of the ninth but managed to pull out the victory to remain undefeated in 51 games this season when they led after eight innings.

Steve Tolleson started the winning rally with a leadoff single against Casey Janssen (4-1). Pennington tried to lay down a bunt but was unable to do it before getting two strikes. After Tolleson advanced on a passed ball by Jose Molina, Pennington was looking to advance the runner with a grounder to the right side.

Pennington did just that and ended up winning the game when the ball made it to right field. Tolleson easily beat Dewayne Wise's throw home to score the winning run.

"At contact, I knew I was going to be able to move him up," Pennington said. "When I looked up and saw where (second baseman Aaron) Hill was playing, I was like, 'That has a chance to get through.'"

Gio Gonzalez allowed two hits in seven innings and Coco Crisp had a homer, two doubles and two RBIs for the A's, who won their sixth straight home series.

"It's good that we're showing signs of life that we're going out there battling and sticking to it," Gonzalez said. "We look at it as a step forward."

Fill-in closer Michael Wuertz was unable to preserve a three-run lead while subbing for injured All-Star Andrew Bailey.

The Blue Jays entered the ninth with just two hits, including an infield popup that was lost in the sun. But Adam Lind started the rally with a double. One out later, Wuertz threw eight straight balls to Lyle Overbay and Edwin Encarnacion to load the bases.

J.P. Arencibia hit an RBI single to make it 4-2 and knock out Wuertz. Jerry Blevins came on and surrendered a tying two-run single to Fred Lewis. Brad Ziegler (3-4) got out of the jam by getting Yunel Escobar to hit into a double play.

"We didn't swing the bats at all well here," manager Cito Gaston said. "We did win one game and came back and tie one up. We just didn't hit the ball like we have been."

Toronto's lone run against Gonzalez was the result of bright sun and a lucky break. With runners on first and second and two outs in the fifth, Lewis hit a high popup in front of the plate. Third baseman Kevin Kouzmanoff and catcher Kurt Suzuki lost the ball in the sun and Lewis got credit for an RBI single.

The only other hit off Gonzalez was Vernon Wells' second-inning double. The left-hander, quietly having a breakout season, struck out six and walked four.

The Blue Jays also lost a fly ball in the sun in the fifth but it didn't hurt them. Crisp was caught too far off second base after the ball fell in shallow left-center and was tagged out in a rundown.

"The sun was in the right spot today for a couple of cheap hits to land in," A's manager Bob Geren said.

Toronto starter Marc Rzepczynski, who had walked only two batters in 18 1-3 innings in the majors this season, walked the first three batters. Suzuki and Kouzmanoff hit run-scoring groundouts to give the A's a 2-0 lead.

Pennington then walked with two outs in the second and scored on Crisp's double. Rzepczynski left after walking Conor Jackson with one out in the fifth for his fifth walk of the game.

"My sinker was either running or sinking straight down especially in the first inning when I was throwing them," Rzepczynski said. "They were either down or away. I just had to relax but I had a hard time throwing a fastball for a strike. Today the fastball was also running and I had no control over it. So when you don't control your fastball it's hard to pitch."

NOTES: Oakland's starters have allowed one or fewer earned runs in eight of their past 11 games. ... Rzepczynski became the first Toronto starter to walk at least five and strike out nobody in a game since Miguel Batista on Aug. 13, 2004, against Baltimore. ... Bailey (rib cage) will make a rehab appearance at Triple-A Sacramento on Friday. ... Arencibia snapped an 0-for-15 slide with his single in the ninth. He was optioned to Triple-A Las Vegas after the game and the Blue Jays will replace him Friday in Boston.