CHICAGO -- Greg Maddux's first two pitches of the fifth inning went flying over the left-center field wall. The second was almost like an instant replay.
"I know Maddux pretty well. I know when he's away and when he comes back inside," said Pena, who also hit a three-run homer in the ninth off Sergio Mitre to finish with four RBI.
Harang (10-12) became the first Reds' pitcher to win 10 games, running his record against the Cubs this season to 3-0 by allowing two runs and eight hits in 8 1/3 innings.
"The fans are enthusiastic, so it's fun to come here and play well. The Cubs have hit me before, but tonight I threw strikes and the guys played defense behind me," Harang said. "And he (Pena) has hit the ball hard all year. I was grateful he did it again."
Harang left after giving up a double to Nomar Garciaparra and RBI single to Jose Macias that made it 5-2 in the ninth. David Weathers got two outs for his 13th save in 16 chances.
Maddux (12-12) had a 1-0 lead and had given up just three singles before Valentin and Pena quickly went back-to-back.
"I got the ball up on one and missed location on another," Maddux said.
Valentin has four homers off Maddux in 10 career at-bats against the 317-game winner.
"It's no secret. I just see the ball good against him," Valentin said. "I'm patient against him and it has paid off."
The loss puts Maddux's record streak of 17 seasons with at least 15 wins in jeopardy. The 39-year-old right-hander will get at least three more starts and maybe four. He lasted seven innings Monday night, giving up five hits and the two runs.
"Sometimes you get outpitched," Maddux said. "You can't control the outcome of the game. You can control what you put into it and that's what I'm going to do, continue to do that until the season is over."
With just 18 games left in the season and two off-days, Maddux might get the extra fourth start if another pitcher is bumped, a scenario that didn't seem to excite him.
"As far as I'm concerned, I've had my chances and I still have a chance, too," Maddux said of the streak. "I mean you got to play the game the right way. I just want to get ready and pitch in five days and do what I can to throw a good game."
After returning home from an 8-2 trip that had them within one victory of reaching .500 for the first time in five weeks, the Cubs took the 1-0 lead on Matt Murton's homer off Harang in the third. But that was all they could muster until the ninth.
Harang, a 6-foot-7 right-hander, did not issue a walk and struck out five, all after the fifth inning.
"He made good adjustments after the first two innings," Valentin said. "When he gives us more than six innings, we have a great shot at winning."
Cubs rookie SS Ronny Cedeno is out for the rest of the season with a broken bone in his left hand, an injury sustained Saturday when he was hit by a pitch from San Francisco's Brad Hennessey. "I can't do anything, that's part of the game," said Cedeno, who plans on playing winter baseball. ... Chicago purchased the contract of INF Ryan Theriot from Double-A West Tenn. Cedeno batted .300 in 40 games in three different stints with the Cubs this season. ... Reds CF Ken Griffey Jr. was out of the lineup for a seventh straight game with a strained right foot. ... Valentin and Pena's homers marked the 10th time this season the Reds have connected back-to-back. Pena's two homers gave him 18 for the season. It was his fourth two-homer game of the season and seventh of his career.