PITTSBURGH -- The fly ball was in Alfonso Soriano's sights from the time it left Nate McLouth's bat with two outs in the ninth inning, the apparent last play of another close Cubs-Pirates game.

Suddenly, the ball disappeared into bright sunshine, and a routine play became anything but that. With it vanished a Cubs lead and, for the second time in less than 24 hours, a game that looked to be won.

Jason Bay beat Chicago with an extra-inning single for the second day in the row, delivering a two-out line drive down the left-field line in the 11th for a 6-5 Pittsburgh victory Sunday after the Pirates tied it on Soriano's dropped fly ball.

Bay hadn't driven in a run with a single this season until doing so in the 14th inning of the Pirates' 5-4 victory Saturday night, also the first time in his career his run-scoring hit ended a game.

The Cubs, 9-3 against the Pirates this season, appeared to have the game won when McLouth lofted a fly ball close to the warning track in left with Chicago up 5-4. But the ball glanced off the heel of Soriano's glove and fell to the grass, scoring pinch-runner Brian Bixler with the tying run.

McLouth was credited with a double, his third hit.

"That gave us an extra gasp of air, and we took advantage of it," Pirates manager John Russell said.

Maybe Soriano can take comfort in this: His drop was reminiscent of a fumbled fly ball by Pirates center fielder Matty Alou on what would have been a game-ending play in a key September 1970 game in Wrigley Field. The Pirates recovered to win the NL East.

"It's very tough when you don't see the ball," Soriano said. "It hit in my glove, but I didn't see the ball. I see very clearly when it got off the bat, but when the ball's coming down it's getting in the sun, so I lose it."

Even worse for the Cubs, they lost the game, too.

"That's going to happen in the game sometimes. We're not perfect," said Carlos Marmol, who also lost a save because of the drop.

Bay, the Pirates' left fielder, was sympathetic.

"We were saying on the bench we hope it doesn't go extra innings because that's the only time of the day the sun is going to be a factor, and sure enough in the ninth it was," Bay said. "When it was hit, I knew it wasn't going to be an easy play."

Cubs manager Lou Piniella could barely tolerate a second extra-inning loss in 24 hours in which the Cubs couldn't hold a ninth-inning lead. Before Saturday, the Cubs were 26-1 when leading going into the ninth.

"Let's forget about what happened and go about our business," he said. "That's all I've got to say about the last two days. Too many mistakes, you're going to get beat in close games on the road."

The Pirates won it after Chris Gomez beat out an infield single to start the 11th against Jon Lieber (2-3), who had pitched 10 1/3 scoreless innings against his former team this season. Bixler bunted him up and, after a Luis Rivas strikeout and a McLouth intentional walk, Bay singled for his sixth hit in two games.

"Two in a career doesn't make me Mr. Walkoff, but back to back is pretty neat," Bay said.

According to the Elias Sports Bureau, Bay is the first major leaguer to decide extra-inning games with hits on successive days since Albert Belle of Cleveland homered in the 14th inning on Aug. 30, 1995, and again in the 10th inning a day later, against Toronto.

Four of the six Cubs-Pirates games in Pittsburgh this season have gone into extra innings, lasting 12, 15, 14 and 11 innings. The six games have lasted 70 innings.

Damaso Marte (4-0) pitched a scoreless 11th inning for the victory, extending the Pittsburgh bullpen's run of scoreless innings in the two games to nine.

The Cubs overcame two solo homers by Rivas and another by Xavier Nady in the first three innings to take a 5-4 lead in the eighth on Derrek Lee's double and Aramis Ramirez's single for his second RBI. Soriano hit a two-run homer, his 11th, and Henry Blanco and Ramirez also drove in runs during a four-run Cubs third against Pirates starter Paul Maholm.

Cubs starter Ted Lilly was 4-0 with a 3.55 ERA in four starts this month before giving up 10 hits and four runs in six innings.

Rivas had homered only 31 times in 1,967 at-bats, an average of one homer every 63½ at-bats, until he went deep in the first and third innings. Piniella argued briefly that Rivas' drive in the first hit the top of the wall and didn't go out, though TV replays appeared to show it striking concrete and bouncing back. Nady hit his eighth of the season leading off the second.

Maholm lasted eight innings, striking out seven and walking two but allowing five runs and eight hits to raise his ERA to 5.11. He is 0-4 with one no-decision this month, surrendering 24 earned runs in 31 1/3 innings, a 6.89 ERA.

Notes

• The Pirates are among the six NL clubs that won't play on Memorial Day.
• The Cubs held out closer Kerry Wood after he pitched two innings Saturday.
• Chicago is 4-4 in extra innings, Pittsburgh is 5-3.
• Soriano has five homers against Pittsburgh this season and seven in 84 career at-bats in PNC Park.
• The Cubs lost successive games to the Pirates for the first time since Sept. 4-5, 2006.
• The Cubs are 0-6-1 in seven road series since they swept three games in Pittsburgh from April 7-10.