The Pittsburgh Pirates haven't finished a season with a winning record since 1992, the last year they made the playoffs, but for most of 2012, the Bucs have been the surprise team of the National League.

But for a team that was alone in first place at the All-Star break, the Pirates are now in free fall mode. Saturday, they're in danger of falling back to .500 for the first time since June 2. They enter play today three games behind St. Louis for the second wild card spot.

Losers of a season-high seven straight contests, the Pirates continue a four- game series against the Chicago Cubs at Wrigley Field. Pittsburgh has lost four in a row to the Cubs, including 7-4 yesterday.

The Pirates have also dropped 10 in a row on the road since winning a 19- inning marathon in St. Louis on Aug. 19.

Starlin Castro hit a three-run home run and drove in four. Anthony Rizzo knocked in a pair of runs and Luis Valbuena scored three times for the Cubs, who have won six of their last seven.

Chris Rusin (1-2) did enough to earn his first big league win, limiting the visitors to two runs and four hits over five-plus innings. He fanned six and didn't walk a batter.

"It felt real good, except for that cold beer shower," Rusin said. "I got ahead of a lot of hitters, kept the ball down and located well."

Carlos Marmol turned in a scoreless ninth for his 20th save.

Pedro Alvarez knocked in two runs, while Andrew McCutchen homered and Gaby Sanchez added an RBI for the Pirates. James McDonald (12-8) didn't make it out of the fourth and was charged with five hits and four runs with four walks over 3 2/3 frames.

"I didn't have any pitches today," McDonald said.

Wandy Rodriguez tries to right the ship for the Bucs this afternoon. The left-hander is 2-0 over his last three starts. He has been charged with three earned runs in his last 19 2/3 innings over three starts. Rodriguez is 6-7 with a 3.84 ERA in 21 career starts versus the Cubs.

Jason Berken will make his first start as a member of the Cubs. The right- hander was claimed off waivers from Baltimore Sept. 7. He has spent the majority of this season with Triple-A Norfolk, going 5-6 with a 3.50 ERA in 26 starts.

Chicago swept the Pirates in three games last weekend at PNC Park. The Cubs lead the season series, 7-6.