CHICAGO (Ticker) -- Adam Dunn broke Bobby Bonds ' single-season strikeout record. He also helped break the spirit of the Chicago Cubs .

Javier Valentin 's two-out, RBI double off Kyle Farnsworth in the 12th inning scored Dunn and lifted the Cincinnati Reds to a 2-1 victory over the Cubs, who lost the last three games of this four-game series.

Chicago (88-71) fell one game behind Houston (89-70) in the National League wild card race. The Cubs play their final three games at home against NL East champion Atlanta, while Houston hosts last-place Colorado.

"It's very frustrating ... to look back and see we lost five of six to the New York Mets and Cincinnati Reds ," Cubs infielder Todd Walker said. "It's very tough. For most of us, it will be difficult for the next few hours and then we will let it go and come back tomorrow and be ready to go."

"It's not over," first baseman Derrek Lee said. "It's obviously a lot tougher after losing today, but it's not over. We just have to win the next three."

After LaTroy Hawkins blew a save opportunity by giving up a two-out, two-strike RBI double to Austin Kearns in the ninth inning Wednesday, the Cubs wasted a brilliant performance by Mark Prior .

Continuing his terrific pitching in September, Prior matched a career-high with 16 strikeouts and allowed just three hits in nine innings. His only mistake was a hanging slider in the seventh to Austin Kearns , who launched it off the left field foul pole, tying the game at 1-1.

"I didn't think it would be close to the pole and then it takes a left turn when it was way out there, so I was just hoping it would hang on," said Kearns, who hit his second homer in as many days.

"I knew it was big game, knew from the minute I started playing catch today I would be locked in," Prior said. "I made two bad pitches out of 110, both to Kearns. One run should have been enough with the stuff I had."

Prior fanned the free-swinging Dunn three times. That gave Dunn 191 strikeouts, two more than the mark set by Bonds in 1970.

"That is the one Bonds that I will have a record over," Dunn joked.

The Cubs had taken the lead in the sixth when Sammy Sosa hit his 573rd career homer, tying him with Harmon Killebrew for seventh place on the all-time list.

But after managing just one run in seven innings against Aaron Harang , who entered the game with a 5.03 ERA, the Cubs were held scoreless over the next five innings by relievers John Riedling , Gabe White , Jose Acevedo and Juan Padilla (1-0).

For the second straight day, the Reds snapped the tie in the 12th. Dunn led off with a single off reliever Mike Remlinger (1-2). Instead of calling on Hawkins, Cubs manager Dusty Baker turned to the hard-throwing Farnsworth, who caught Kearns looking at a called third strike.

Dunn stole second and went to third on a groundout by Darren Bragg before Farnsworth hung a slider to Valentin, who hit a line drive that bounced to the right field wall.

"I know he is a tough guy and a good reliever," Valentin said. "So I went up looking for one pitch and he threw me a slider down the middle, and I made good contact."

The Cubs put runners on first and second with two outs in the bottom of the 12th, but Moises Alou flied out.

"It's tough to lose two one-run 12-inning games in two days," said Cubs manager Dusty Baker , whose club fell to 19-29 in one-run contests. "We had bases loaded three times. It's tough to lose these type of games down the stretch here."

The first two times Chicago loaded the bases with two out, Prior struck out in the second and bounced into a force play in the fourth. Michael Barrett fanned with the bags full and two out in the 11th.

"I came up with bases loaded twice and wanted to find a hole somewhere, but I can't speak much about that," said Prior, whose batting average dropped to .139. "I just concentrated on putting up zeros."