Chicago Cubs second baseman Mike Fontenot bobbles the ball after trying to tag out Pittsburgh's Andrew McCutchen during the second game of Wednesday's doubleheader at Wrigley Field. The Pirates won the second game 8-2 after pinning a 4-0 loss on the Cubs in the first game.

CHICAGO — Ryan Doumit and the Pittsburgh Pirates had a quite a day at Wrigley Field.

Doumit collected four hits and four RBI to help the Pirates beat the Chicago Cubs 8-2 Wednesday night for a doubleheader sweep.

"Hey, that's baseball," Doumit said. "To have a day like this, I can't remember the last time we won at Wrigley, let alone two games in one day."

The Pirates had won only once in Chicago this season, on May 25. Their last doubleheader sweep at the Cubs' cozy ballpark was June 20, 1983, before many of the current Pirates were born.

Jeff Karstens tossed five innings for the second victory by a no-name Pittsburgh pitcher over a high-priced Cubs starter on the day. A few hours before Karstens beat Carlos Zambrano, Charlie Morton threw a four-hitter in a 4-0 victory over Ted Lilly.

While Karstens and Morton make just over $400,000 each, the combined 2009 salary of Zambrano and Lilly is $31.75 million — or about $577,000 per start.

Doumit went 4 for 4 with his 10th homer in the second game. Jason Jaramillo, who backs up Doumit at catcher, had a two-run double in the opener.

"To sweep a doubleheader is tough anywhere, home or road," Pirates manager John Russell said. "To come in here and beat two really good pitchers ... I'm really proud of the way the guys battled."

Zambrano (9-7) gave up four runs and six hits with four walks over six innings in his final outing of a frustrating season. The right-hander failed to post double-digit victories for the first time in his seven years as a full-time starter.

The leader of a rotation that had carried the Cubs to the 2007 and 2008 NL Central titles, Zambrano recently said he would retire if he has a similar season next year — even though he still would have two years left on his $91.5 million contract.

Karstens (4-5), who has pitched mostly in relief this season, allowed two runs and five hits. Morton (5-9) was dominant in the opener, shutting down the same Chicago team that lit him up for 10 runs seven weeks earlier.

"I try not to put so much emphasis on one game," Morton said of the 17-2 loss on Aug. 14. "But it's a big step in the sense that, yeah, I came here and gave up 10 runs in an inning. This time ... I was throwing pretty much everything for strikes. Just being more aggressive with my pitches."

The 25-year-old right-hander, acquired in the June 3 trade that sent Nate McLouth to Atlanta, had a career-high eight strikeouts, walked three and hit two batters. Morton had never thrown more than seven innings in a game.

"You take away the (Aug. 14) start," Russell said, "and his numbers have been pretty good."

Morton had a 3.66 ERA in his other 17 starts.