The Pirates, meanwhile, are in a skid that has lasted more than a month. The Bucs are 14-24 since July 29. They are now in danger of being swept in PNC Park for the first time this season.
The Pirates will turn to rookie left-hander Jeff Locke as they try to avoid the sweep. Locke will be making his second start of the season.
Locke gave up five runs on seven hits in five innings in the Pirates' 5-1 loss to the Astros on Monday. Manager Clint Hurdle said he felt that Locke pitched well, despite taking the loss.
"He used his fastball very well, he changed speeds," Hurdle said. "He should walk away knowing he did some good things out there."
The Cubs will send Chris Rusin, another rookie left-hander, to the mound Sunday. It will be his third career Major League start. In his last outing, Rusin allowed five runs on eight hits and lasted just one-plus inning.
Rusin said the cause of his problems on Tuesday was poor location.
"I just didn't keep it down, and when I missed my spots, they capitalized," Rusin said. "They did what they were supposed to do, so I give them credit. This is the big leagues, and you can't miss your spots here, because that will happen."
Pirates: McCutchen goes back to work after streak ends
Pirates center fielder Andrew McCutchen saw his streak of reaching base in 40 straight games against the Cubs come to an end Friday night, but made sure not to repeat the feat.
McCutchen was hit by a pitch in his first plate appearance of the Pirates' 4-3 loss on Saturday. He has now reached base safely in 47 of his 51 career games against Chicago.
McCutchen went 0-for-3 with three strikeouts, but scored his 94th run of the season, adding to his National League-leading total.
Cubs: Jackson day to day after collision Friday night
While making a catch to end the sixth inning Friday night, center fielder Brett Jackson ran face first into the center-field fence at PNC Park in the Cubs' 12-2 victory. The rookie had to leave the game due to a few bruises and scrapes, and was out of the lineup again Saturday.
Jackson is listed as day to day. Cubs manager Dale Sveum said he didn't want to take any aggressiveness out of Jackson's game.
"That's the kind of player you want, but there does come the risk factor of injury when you do that," Sveum said. "That's why, with the last couple years with Carlos Gomez playing like that in Milwaukee, they're bound to get hurt. The speed they create and the running, whether it's diving on the bases when they're running, and the fearlessness they have of walls, sometimes it's just a matter of time before something happens."
Sunday will be the team's final meeting at PNC Park this season. Each team has four victories.
After concluding this weekend's series Sunday, the two teams will meet again in Chicago for a four-game series starting Friday. The Cubs and Pirates will play seven games against each other in 11 days.