Chicago ? Mark Prior pitched his best game of the season. Still, he couldn’t stop the Chicago Cubs’ final-week slump that has damaged their chances of making the postseason.

“It’s not from a lack of preparation. It’s not from a lack of trying. It just hasn’t worked out. I don’t have a philosophical quote about it. We lost,” Prior said Thursday after the loose and pressure-free Cincinnati Reds beat the Cubs in 12 innings for the second straight day.

Chicago fell for the fifth time in six games and dropped a game behind idle Houston for the NL wild card.

Javier Valentin hit a two-out double in the 12th to give Cincinnati a 2-1 victory, wasting Prior’s stellar nine-inning effort that saw him tie his career high with 16 strikeouts.

“I think we all know where we’re at right now,” Prior said. “I could care less about me personally. It’s not about me.”

It’s mainly about the Cubs’ offense — or lack of it.

Chicago had the bases loaded three times and didn’t score, and stranded 12 runners.

“It’s tough to lose two 12-inning games in a row, especially when we had opportunities to win the game,” a dejected Cubs manager Dusty Baker said. “It’s tough to lose like this down the stretch.”

Adam Dunn, who earlier broke Bobby Bonds’ major-league record for strikeouts in a single season when he fanned in his first two at-bats, singled in the 12th off Mike Remlinger (1-2). Dunn stole second and moved to third on a grounder before Valentin doubled to right off Kyle Farnsworth.

“We beat these guys. We won three out of four and, here in Chicago, that is tough,” Valentin said.

“Obviously it’s tough on them and the town, but we can’t come in here and just roll over,” said Cincinnati’s Austin Kearns, who homered off Prior.

Chicago loaded the bases for the third time in the 11th, but Juan Padilla (1-0) escaped by striking out Michael Barrett.

Pinch-hitter Jose Macias singled to start the bottom of the 12th and reached second on a one-out sacrifice by Nomar Garciaparra. Aramis Ramirez walked before Moises Alou flied to center to end the game and perhaps Chicago’s chances of returning to the postseason.

Garciaparra said he bunted with one out and Reds third baseman Felipe Lopez back because he was hoping for a hit or to at least move Macias into scoring position. But like most everything the Cubs tried, it didn’t work.

“Surprised? Absolutely surprised,” Garciaparra said of the Cubs’ precarious standing as they get ready for a closing three-game series with the Braves.

Giants 4, Padres 1

San Diego — Jerome Williams pitched seven strong innings in his first start in two months, and San Francisco jumped back into a tie for the wild-card lead by beating San Diego. The Giants (89-70) tied the idle Houston Astros in the wild-card race, one game ahead of the Chicago Cubs (88-71).

The Padres, playing their home finale, were pushed to the brink of elimination, falling three games back in the wild-card race with three to play.

Barry Bonds beat out an infield single in the eighth, making him 1-for-10 in the series.

Dodgers 4, Rockies 2 11 innings

Los Angeles — Light-hitting David Ross hit a two-out, two-run homer in the 11th inning, and Los Angeles beat Colorado to clinch no worse than a tie for the NL West title. Ross, batting just .169, hit a 2-1 pitch from Steve Reed over the left-field wall after Alex Cora was hit by a pitch from Brian Fuentes (2-4). It was Ross’ first at-bat of the game and his fifth homer of the year.

The Dodgers, who had rallied from a 2-1 deficit in the 10th inning, mobbed Ross at the plate and the sellout crowd of 53,438 stood and cheered for several minutes.

Brewers 7, Cardinals 6

St. Louis — Matt Morris struggled in his final tuneup for the playoffs, and Milwaukee beat St. Louis to send the NL Central champion Cardinals to their first four-game losing streak of the season. Keith Ginter hit a three-run homer in the first inning, and Scott Podsednik hit a two-run shot in the fourth.

Phillies 7, Marlins 4

Philadelphia — Pat Burrell went 4-for-4, including a tiebreaking two-run single in Philadelphia’s six-run seventh.