CINCINNATI -- To this point, the Chicago Cubs' postseason pitching plans centered around Jake Arietta and Jon Lester.

Beyond the top two, the Cubs are auditioning arms. Manager Joe Maddon liked what he saw from right-hander Dan Haren on Tuesday night.

Haren pitched seven shutout innings, and catcher Miguel Montero sparked a four-run first with a two-run double, lifting Chicago to a 4-1 victory over the Cincinnati Reds in the opener of a three-game series at Great American Ball Park.

"That's the best he's thrown the ball for us," Maddon said of Haren. "He had great carry on the ball. You could see by the swings that there was something different from him tonight."

The first pitch of Tuesday's game was delayed two hours and 31 minutes by rain.

When things finally got underway, Haren was in control throughout. The right-hander had five 1-2-3 innings and allowed just three hits. He did not walk a batter, and he fanned six.

Haren (10-9) retired 12 straight before center fielder Jason Bourgeois beat out an infield grounder with two outs in the sixth.

"He has the experience, too," said Maddon, when asked about Haren's playoff prospects. "He looked good tonight."

Before Tuesday, Haren hadn't pitched since Sept. 18, throwing three side sessions in the interim.

"I felt fresh coming in," Haren said. "The last few times I've felt a lot better. Kept us in the ballgame and had pretty good stuff."

It was Haren's longest outing since May 18 and his fewest hits allowed since June 14.

"He's a pro," Reds manager Bryan Price said. "I've seen him a long time, and he's been real good. When he's on, he's very tough."

Montero went 2-for-3 with a double and two walks for the playoff-bound Cubs, who improved to 11-6 this season against the Reds. Chicago (92-65) pulled within three games of Pittsburgh in the race for the second National League wild card. The Pirates' scheduled home game against the NL Central-leading St. Louis Cardinals was rained out.

Cubs left fielder Kyle Schwarber, playing 40 miles from his hometown of Middletown, Ohio, reached base four times via two hits and two walks.

The Reds (63-94) saw their losing streak reach 10 games, their longest since an 11-game skid in 1998.

Chicago was on the verge of extending its scoreless innings streak to 30, but Austin Jackson, who entered the game as a defensive replacement in right field, misplayed a ninth-inning fly ball, allow Bourgeois to reach third. Bourgeois later scored on a groundout by third baseman Ivan De Jesus.

Cubs reliever Travis Wood entered and induced a game-ending double-play grounder from the only batter he faced, second baseman Skip Schumaker, to earn this third save.

The Cubs came out swinging following the rain delay.

Montero's two-run double was the key blow in a four-run first inning against Reds rookie right-hander Josh Smith.

Second baseman Tommy La Stella added a sacrifice fly and shortstop Javier Baez an RBI single for the Cubs in the first.

Smith managed to salvage five innings from his start despite making 101 pitches. He allowed four runs on six hits and five walks while striking out seven.

"That was big, not only for me, but for the guys in the bullpen," Smith said of getting through the fifth. "(The relievers) have been used a lot lately. I wanted to go at least six, but it was big to get five after that debacle of a first inning."

The Reds were short-handed after third baseman Todd Frazier left the game in the fourth inning with a slight strain of his right Achilles tendon. He was hurt on a sliding attempt to catch a foul pop.

Haren says he is not pondering a potential postseason role just yet.

"I don't want to think about it," he said. "I'll be in the dugout regardless. If they need, they need me. I'll be ready if they call my number."

NOTES: Reds CF Billy Hamilton underwent successful arthroscopic surgery on his right shoulder Tuesday. He is expected to resume baseball activity in four to six weeks. ... Cincinnati's 18 rain delays this season at Great American Ball Park (totaling 26 hours and 57 minutes) represent the highest total at home since the Reds started tracking weather delays in 1978. ... The Cubs are 11-6 against Cincinnati with two games remaining, their first season series victory against the Reds since 2009. ... According to the Elias Sports Bureau, Cubs OF Chris Denorfia became the first pinch hitter in major league history to hit a walk-off homer for the only run of an extra-inning victory Monday in Chicago's 1-0, 11-inning win over the Kansas City Royals.