CHICAGO (Ticker) -- Mark Prior has the Chicago Cubs on the verge of going to a place they don't go often.

The red-hot Prior struck out 10 over 6 2/3 innings as the Cubs clinched a tie for the National League Central Division title with a 4-2 victory over the Pittsburgh Pirates in the first game of a doubleheader.

Needing to sweep the doubleheader and a loss by the Houston Astros to clinch their first division title since 1989, and just their fourth playoff appearance since 1945, the Cubs had the right guy on the mound in the opener.

A 23-year-old righthander, Prior (18-6) had to work for the ninth win in his last 10 starts. He allowed two runs and seven hits, walking two while throwing 133 pitches.

"I didn't feel as strong as I would have liked or as comfortbale as I would have liked," Prior said. "But I just worked with Damian (Miller), who called a great game."

Kyle Farnsworth worked 1 1/3 scoreless innings and Joe Borowski pitched out of trouble in the ninth for his 33rd save in 37 chances.

While Prior and the bullpen did the job, the Cubs (87-73) also received the necessary help from the Brewers, who posted a 5-2 win over the Astros (86-75).

"Everybody's into it, the whole town is into it and I think everybody is rooting for the Cubs," Chicago manager Dusty Baker said.

Pirates starter Josh Fogg (10-9) surrendered four runs and six hits over six innings, walking two and striking out three.

"It's a great environment, but not when you lose," Fogg said. "I wasn't worried about the scoreboard, just getting outs."

After Pittsburgh stranded a runner in scoring position in each of the first two innings, it broke on top with one out in the fourth on Craig Wilson 's 18th homer.

But the Cubs, who managed one hit through three innings, responded in the bottom of the fourth.

Mark Grudzielanek led off with a single and Fogg walked Sammy Sosa and Moises Alou . Former Pirate Aramis Ramirez bounced into a forceout to plate a run and Randall Simon followed with a sacrifice fly, giving the Cubs a 2-1 lead.

Prior, who had to battle for much of the day, had one of his easiest innings in the fifth when he struck out a pair.

In the bottom of the inning, Miller led off with his ninth homer and Prior and former Pirate Kenny Lofton singled. After Grudzielanek sacrificed, Sosa lofted a sacrifice fly to make it 4-1.

The Pirates got back a run in the sixth on Rob Mackowiak 'a RBI single. But with two runners on, Prior got Jack Wilson to bounce into an inning-ending forceout.

After issuing a two-out walk to Abraham Nunez in the seventh, Prior departed to a standing ovation.

Borowski easily retired the first two batters in the ninth before Tike Redman reached on an infield hit and pinch hitter Carlos Rivera walked. But Borowski got Jason Kendall to pop out to second to end it.

"It was a good game, we just didn't get the big hit when we needed it," Pirates manager Lloyd McClendon said.