CINCINNATI (Ticker) -- Sean Casey and the Cincinnati Reds are making dramatic victories look routine.

Casey plated Wily Mo Pena with a double to left-center field against Todd Wellemeyer in the bottom of the 10th inning as the Reds edged the Chicago Cubs , 2-1.

It was the Reds' major league-leading 18th victory in their final at-bat and their ninth walk-off win. Casey was the last to accomplish the feat, with an RBI single in the ninth inning that beat Toronto on June 7.

The Reds improved to 8-2 in extra-inning contests while the Cubs fell to 6-2.

Pinch hitter Russell Branyan began the bottom of the 10th inning with a walk against Mike Remlinger (4-1) and Barry Larkin advanced pinch runner Pena with a sacrifice.

"Rem's been doing so good," Cubs manager Dusty Baker said. "He had (Branyan) 1-2 one. Leadoff walks will kill you every time."

Wellemeyer induced Jose Guillen to line out to right before Casey - who had been 0-for-4, including three strikeouts on nine pitches - rapped a double into the gap to even the four-game series at one game apiece.

"I had a talk with him before the game," Reds manager Bob Boone said of Casey. "I talk to him about every four weeks or so. Every time he gets a couple of hits. This time I didn't think it was going to work. We had to go to extra innings before it worked."

"I pumped my fist and (Reds third baseman Aaron Boone ) came running out to jump on my back," Casey said. "It was an exciting game. With the adrenaline I probably could've carried a truck."

Baker said he decided to have Wellemeyer pitch to Casey rather than intentionally walk him to get to Reds cleanup hitter Austin Kearns .

"We had a decision to make in the 10th," Baker said. "Do we walk Casey, who is going to make contact, or (face) Kearns, the RBI leader in the league? It was a choice between the dagger or the sword and the dagger got us."

Scott Williamson (4-2), who walked three batters but did not allow a hit in the ninth and 10th innings, picked up the victory.

Both starting pitchers were sharp. Chicago's Carlos Zambrano yielded one run and four hits in a career high-tying eight innings, while Cincinnati's Ryan Dempster gave up one run and six hits in seven frames.

"Everything was good today, especially the slider," Zambrano said. "I had my best stuff today. Now, I have to continue to do better and better every time."

Dempster was making his third start since a 15-day stint on the disabled list with an inflamed nerve in the right side of his neck.

"He's back to the way he was in spring training," Bob Boone said of Dempster. "I expect to see Ryan like this. I don't know about shutting them out but this is what I expect to see the rest of the year. He was under control, making pitches. He's a horse. He's one guy that I don't worry about his pitch count."

"That's what's been missing when I wasn't healthy," Dempster said of his ability to pitch late into games. "I wasn't able to give them the innings that they wanted when they traded for me (from Florida last season)."

Chicago played its final contest without superstar Sammy Sosa , who completed a seven-game suspension for using a corked bat. The Cubs went 3-4 without their right fielder.

After Cincinnati second baseman Juan Castro flied out to end the bottom of the ninth, he got into an argument with plate umpire Joe West. Bob Boone stepped in to protect Castro and got ejected for the first time this season.

Chicago took a 1-0 lead in the top of the fifth when Zambrano led off with a double against Dempster, advanced to third on Tom Goodwin 's flyout and scored on Corey Patterson 's two-out double to right.

Cincinnati tied the contest in the bottom of the frame when Castro hit a one-out double and came home on Larkin's two-out single to center.