Starlin Castro and Jorge Soler each drove in two runs, and Anthony Rizzo was 4 for 5 with two runs scored as the Chicago Cubs (58-47) won their sixth straight game with a 5-0 shutout of the Pittsburgh Pirates (61-44) Tuesday night. 

Castro had a pair of RBI doubles -- one each in the third and fifth innings -- after failing to bring in a run with the bases loaded and one out in the first. Both doubles scored Rizzo, who had also doubled each time, to give the Cubs their second and fourth runs of the night. Rizzo also had two singles.

After a long slump, Rizzo is hitting .418 with four home runs, 10 RBI, and eight runs scored in his last eight games.

Soler walked with the bases loaded in the first for the Cubs' first run and singled home Kris Bryant in the sixth to tally their final run. Catcher David Ross followed Castro's first RBI double with a run-scoring single in the third.

Cubs starter Jake Arrieta (W: 12-6, 2.50 ERA) dominated once again, limiting the Pirates to just two singles in seven innings. He walked three and struck out five.

Arrieta is seventh in the National League among qualifiers for ERA. Tuesday night's was his ninth straight quality start (6-1 record in that stretch) and 18th of the season in 22 starts. MLB.com's Cubs beat writer Carrie Muskat quoted manager Joe Maddon describing the potential that Arrieta, age 29, has still yet to realize. Said Maddon,

"He is not there yet. He's not as good as he's going to become. When he really understands how to utilize all his weapons, it can get scary. It's all there. I'm not complaining. The guy has been fabulous. But I'm saying there is another level of Arrieta over the next couple years."

J.A. Happ (L: 4-7, 4.78) took the loss in his Pirates debut. He allowed four earned runs on eight hits in 4 1/3 innings. He walked two and struck out six.

With the win, the Cubs pull to within three games of the Pirates for the top N.L. Wild Card position and 8.5 games of the division-leading St. Louis Cardinals. The Cubs also hold a 1/2-game lead over the San Francisco Giants for the second wild card spot.

On Wednesday, new Cub Dan Haren (7-7, 3.42) will make his first start for the Cubs since coming over from the Miami Marlins last week. Lefty Jeff Locke (6-6, 4.21) will start for Pittsburgh. The game begins at 7:05 p.m. EDT.

The Cubs are 14-8 against left-handed starters, and they will look for the two-game sweep of the rain-shortened series. Rain washed out Monday night's game in the fourth inning.