The Mariners don't have to go far back in their memory banks to remember the agony of a walkoff loss.

But on Wednesday night, the M's seemed to have an exhilarating win in their back pockets when Jason Bay led off the ninth with a tiebreaking home run.

Yet doom still loomed for the Mariners, who gave up the tying run in the ninth and the game-winner in the 10th on a bases-loaded, no-out single by Will Venable off reliever Yoervis Medina.

That resulted in a 3-2 loss to the Padres at Petco Park, and the Mariners' fourth walkoff defeat in their past seven road games.

Their road losing streak, walkoff or otherwise, extended to seven, and they've dropped 10 of their past 12 overall.

Having the near-victory snatched away seemed to make it all the more agonizing. Brendan Ryan labeled the losses "unbelievably frustrating."

After Bay's homer in the top of the ninth gave Seattle a 2-1 lead, closer Tom Wilhelmsen could not get the final outs in the bottom of the inning. It was his second blown save of the season.

"Tommy's been great all year," Mariners manager Eric Wedge said. "He just had a tough day."

He started ominously by walking Yasmani Grandal, then gave up a single to Jedd Gyorko — the first hit Wilhelmsen has given up to a right-handed hitter all season. They had been 0 for 33.

Things only got worse when a passed ball by catcher Kelly Shoppach moved runners to second and third. After an intentional walk loaded the bases with no outs, Kyle Blanks delivered a sacrifice fly to center to tie the score, with Gyorko moving up to third.

Wilhelmsen at least kept the game alive by getting Alexi Amarista to pop out and pinch-hitter Carlos Quentin to ground out. But that life didn't last long. Chris Denorfia led off the 10th against Medina with an infield single after Ryan just missed a dazzling play on a between-the-legs stop. His spinning throw was wild.

Everth Cabrera followed with a hit-and-run single — right to the spot vacated by Ryan as he covered second as Denorfia took third. The Mariners walked Chase Headley, last year's RBI champion in the National League, to load the bases. Venable laced a hard grounder that glanced off the glove of first baseman Kendrys Morales into short right field as Denorfia scored easily to win it for San Diego.

Ryan was kicking himself after the game, both for not completing the difficult play on Denorfia, and for not changing the coverage on the steal attempt so that second baseman Nick Franklin covered.

"Oh, man. I don't know how I'm going to sleep tonight after that," Ryan said. "It's a makable play. Got to it, had it clean, good transfer. I've made that throw a million times.

"I feel bad for Medina. He's going to have an L next to his name, but three ground balls. Granted, the last one's hit hard, but I want to take full responsibility. That leadoff guy should have been out.

"There's only two things that are going to happen after that — they're going to bunt it, or slash hit-and-run it. I was not caught off guard there. I should have switched the coverage. I should have stayed home. Then we at least get one, or maybe get sneaky and get two out of it. That whole inning could have been completely different, and I feel like that was all me."

The Mariners managed just four hits in the game, and struck out 13 times.

"We've had some tough losses these first couple of months," Wedge said. "I mean, some tough ones. The worm will turn. It will come back around. We have to keep fighting."