PITTSBURGH -- The Pittsburgh Pirates are playing out the string and giving experience to some younger players down the stretch. The youngsters came through in a big way Monday.
Arrieta lasted just 2 1/3 innings before grabbing his hamstring in pain after a pitch. He attempted one more pitch under the eye of trainers before again grabbing his hamstring and removing himself from the game.
Bell hit a two-run homer in the first inning off Arrieta (14-9) and added an RBI single in the fifth. He had a run-scoring groundout as part of Pittsburgh's seven-run eighth inning.
Moroff hit a solo home run in the third and an RBI double in the seventh as the Pirates built a 5-0 lead off Arrieta and relievers Justin Grimm and Rob Zastryzny, who were pressed into early duty. Moroff added a two-run single in the eighth.
"It was a good day for Pirate baseball," Pittsburgh manager Clint Hurdle said. "It was a good day for those young men to go out and compete. It was a good day for our team, Chad Kuhl in particular, as well."
Kuhl (7-10) pitched seven scoreless innings, striking out eight while allowing just four hits and two walks. It was Kuhl's first win in six career starts against the Cubs. He had an 0-4 record with an 11.07 ERA against them coming into the game.
"It was a good one for all of us," Bell said. "Kuhl started us off. We jumped on Arrieta early. Throughout the course of the game, it was a lot of hard-hit balls and a lot of good defense."
Arrieta was checked out by the Pirates' physicians and said that an MRI exam may be required after a re-evaluation on Tuesday, but he is optimistic that he will be able to make his regular turn in the rotation.
"I never really had a hamstring issue before," he said. "It's kind of a foreign feeling. I think it could have been a lot worse. No pop or anything like that. ... It's unfortunate, but I think it's going to be OK."
Chicago maintained its 3 1/2-game lead atop the National League Central with the Milwaukee Brewers also losing Monday.
The Cubs advanced just one runner beyond second base against Kuhl. Ben Zobrist led off the second inning with a single and tried to score from second on Mike Freeman's single to left, but he was thrown out at the plate by Starling Marte.
In the eighth, the Pirates piled on against reliever Dillon Maples and outfielder Leonys Martin, who was called on to finish the frame.
Elias Diaz hit an RBI double and Moroff added a bases-loaded, two-run single. Andrew McCutchen singled home a run off Martin, and Bell drove in a run with a groundout before David Freese hit a two-run homer.
"There was a limited bullpen tonight," Cubs manager Joe Maddon said, explaining the use of Martin. "He said he's been trying to do that for a bit; nobody ever put him in, and he got his opportunity today on national TV."
A.J. Schugel and Dovydas Neverauskas each pitched a scoreless inning of relief to preserve the shutout.
NOTES: The Pirates claimed LHP Jack Leathersich off waivers from the Cubs and optioned him to Triple-A Indianapolis. Leathersich was 2-4 with one save and a 2.84 ERA in 41 games with Triple-A Iowa. ... Pittsburgh RHP George Kontos (right groin strain) will face live batters Tuesday and should be activated from the disabled list Wednesday if all goes well. ... Chicago SS Javier Baez was scratched after getting into an ugly collision at second base against Atlanta on Sunday. Baez slid face-first into Braves 2B Ozzie Albies. Afterward, he experienced blurred vision and an injured left thumb. His vision has cleared, but the thumb injury kept him out Monday. He hopes to play Tuesday. ... Cubs C Willson Contreras (right hamstring strain) ran the bases, and the team hopes to be able to send him on a rehab assignment before the minor league season ends.