Playing without third baseman Adrian Beltre, a game-time scratch, the Mariners led 4-1 heading into the bottom of the eighth and 4-3 entering the bottom of the ninth. But Batista (3-9) allowed a leadoff walk to Kelly Johnson and then a game-tying double to former Mariner Greg Norton. After an intentional walk and a hit-batsman loaded the bases, Batista surrendered a broken-bat, game-winning single to catcher Brian McCann that fell just over second baseman Jose Lopez's head.
The rally made a winner of Blaine Boyer (2-5), who pitched a scoreless ninth inning.
"The whole fault was mine," Batista said. "If I did my job, it would be a different story."
While the ending wasn't right, Batista insisted he had all the ingredients for a happy ending, including the 2-2 fastball that Norton ripped into the gap in right-center.
"I wanted Norton to pull the ball and he did," said Batista, who is now tied for second with Detroit's Justin Verlander for the most losses in the American League. "He just pulled it up in the air. He hit it right over Lopez's head, right where we wanted the ball to go. He just did a good bit of hitting."
The loss was only the Mariners' third in 24 games when leading after eight and spoiled a superb effort by Washburn.
The Braves, with starters Chipper Jones and Yunel Escobar limited to pinch-hitting roles, won for the first time in 30 tries when trailing after eight.
After eight, the Mariners were still in front, but were reeling. Following a long home run by Ruben Gotay off Sean Green, shortstop Betancourt made a remarkable barehanded grab of a Gregor Blanco grounder but threw wildly past first baseman Richie Sexson. The ensuing ricochet into foul ground down the right-field line allowed Blanco to reach third, from where he would score on a pinch-hit single by Jones off Arthur Rhodes.
Jones had been 0-for-3 with two strikeouts lifetime against Rhodes.
"He had him," Riggleman said of the errant throw. "The thing he was upset about was he didn't have the ball good in his hand. If he had the grip on ball that he wanted, he wouldn't have thrown the ball like that. I was amazed that he picked it as clean as he did barehanded."
The bullpen's failure and the M's inability to add more than one run after the first -- on a Betancourt single -- wasted a brilliant effort by Washburn, who allowed only a first-inning run while throwing a season-high 118 pitches, 74 of which were strikes. He surrendered two runs or fewer for the fourth time in his last five starts.
"Tonight was crazy that I struck so many guys out," said the Mariners' lefty, who has a 3.10 ERA over those last five starts.
He credits the success to a mechanical adjustment following a call to his college coach Tom Lechnir.
"Usually I don't strike anyone out," Washburn said. "I make the guys put it in play and end up giving up quite a few hits and pitch with guys on base. That's just normal for me. But I was able to get out of some jams and limit the damage there in the first inning and keep us in the ball game. It just didn't end up with us on top."
Reliever Roy Corcoran also helped limit the damage, coming in with two outs in the sixth and runners on first and second. He retired pinch-hitter Escobar on a soft grounder to second to end the threat.
Before that, though, it didn't look like Washburn or Atlanta starter Jair Jurrjens would get out of the first inning.
The Mariners came out of the 32-minute frame with a 3-1 lead, taking advantage of a pair of errors by shortstop Omar Infante to plate three first-inning runs off Jurrjens. Jeremy Reed drove in the first run with a sacrifice fly to center. Then, after Infante's second error, Betancourt's single to right made it 3-0.
Jurrjens allowed the three runs, all unearned, despite limiting the Mariners to only three hits over six innings.
Ichiro Suzuki had two hits for his 23rd multi-hit game of the season, tied with Lopez for the most on the Mariners.
Ichiro also stole his 31st and 32nd bases of the season.
While Riggleman applauded the team's effort, there was a feeling that this one, like too many this season, got away.
"Any time you're winning in the ninth and then you lose, it's tough," he said. "I think our guys are really competing out there. The energy is good, they're playing hard, they're running hard, sliding hard. They agonize over that loss right there. That's the way it should be."
"This has been a tough season for us," Washburn said. "We've had, unfortunately, quite a few games where we should have won it but at the end we found a way to lose."