Jake Arrieta shut down his former team, holding Baltimore to four hits in seven innings and Javier Baez homered again as the Cubs beat the Orioles 4-1 on Friday.
Baez hit his sixth homer in his 18th game since getting called up from Triple-A, Luis Valbuena also homered, and Logan Watkins and Arismendy Alcantara each drove in runs with singles as the Cubs snapped AL East leading Baltimore's four-game winning streak.
The Orioles traded Arrieta to Chicago with reliever Pedro Strop in a multi-player deal during last season. He's turned into Chicago's ace this season.
Baltimore's Nelson Cruz hit his major league-leading 34th homer, a solo shot off Arrieta (7-4) in the seventh.
Baltimore's Kevin Gausman (7-5) allowed three runs on six hits through five innings, He struck out seven.
Hector Rondon pitched a perfect ninth for his 20th save.
Arrieta retired the first 13 Baltimore hitters before Chris Davis lined a solid single to center with one out in the fifth, one of only two innings when the Orioles managed baserunners against Chicago's 6-foot-4 right-hander. He struck out five and walked only one.
Valbuena, batting cleanup with Starlin Castro out due to a family emergency, tied a career-high with his 12th homer that put the Cubs ahead 1-0 in the fourth. Ryan Sweeney doubled one out later, then scored on Watkin's single.
Davis was thrown out at the plate in the fifth on strong throw from Sweeney in right field when he tried to score on Caleb Joseph's sharp single, the Orioles' second hit.
Baez hit a towering shot just inside the left-field foul pole, on a 3-2 pitch with two out in the fifth to make it 3-0.
Cruz ended Arrieta's shutout bid with a homer that reached the left field basket.
Orioles: 2013 Gold Glove-winning 3B Manny Machado, on the DL (right knee ligament sprain) since Aug. 13, has not resumed baseball activities and will not be available when he is eligible to return on Aug. 27, Orioles manager Buck Showalter said before the game. "We'll probably have updates in the next two days about where he is, and I'll talk to him today," Showalter said.
Machado sprained his knee in a while taking a swing in a game versus the Yankees on Aug. 11. He is hitting .278 with 12 homers and 32 RBIs in 82 games. He missed the first month of the season while recovering from surgery on his left knee.
Cubs: RHP Brian Schlitter, on the DL since Aug. 10 (right shoulder inflammation) has resumed throwing and made a relief appearance with the Cubs rookie league affiliate in Mesa, Arizona, on Thursday night.
Orioles RHP Bud Norris (11-7, 3.69) faces Cubs RHP Kyle Hendricks (5-1, 1.48) on Saturday at 1:20 p.m. CDT. Hendricks has six straight quality starts since rejoining the Cubs on July 22.