CHICAGO -- Jake Arrieta relished the chance to face his former team on Friday, but it wasn't long before it became just another game.

The right-hander struck out five and allowed just four hits in seven innings in his first appearance against the Baltimore Orioles as the Chicago Cubs claimed a 4-1 victory in the opener of a three-game interleague series.

"There was a little more to it being your former team, but after the first inning it was kind of business as usual," Arrieta said. "It was nice to face those guys. It's good to see a lot of them again. It's been awhile."

Arrieta, acquired in a trade with the Orioles in July 2013, allowed a seventh-inning home run to major league leader Nelson Cruz and improved to 7-4 for only his second win since late June.

Right-handed reliever Hector Rondon worked a perfect ninth inning for his 20th save.

Orioles starter Kevin Gausman (7-5) took the loss in a five-inning outing.

Cubs third baseman Luis Valbuena went 2-for-4 with an RBI and scored a run.

Chicago broke a scoreless tie in the fourth inning with Valbuena's 12th home run of the year, a solo shot to right-center field for a 1-0 lead. Then with two outs, right fielder Ryan Sweeney doubled to left and came home on second baseman Logan Watkins' base hit to deep right center to make it 2-0.

Arrieta held the Orioles hitless until the fifth inning when third baseman Chris Davis singled to center with one out. Davis advanced to second and bolted for home on catcher Caleb Joseph's base hit to right. But Sweeney fired a perfect throw to catcher John Baker, who tagged Davis at the plate.

The on-target throw was one of several defensive plays that prevented runs or kept the Orioles off the bases.

"You've got to tip your hat to them, they played really good defense," Orioles manager Buck Showalter said. "You take those four, five or six the other way ... and I know what it feels like on the other side of it because we've been able to play some pretty good defense along the way."

In the bottom of the inning, Chicago shortstop Javier Baez collected his sixth home run in his first 18 games, going deep with two outs on a 3-2 count to make it 3-0.

"It feels great, I'm going to keep fighting to hit the ball hard," Baez said. "I'm not afraid to strike out, so I'm going to keep swinging the bat."

Gausman closed his day with three earned runs and six hits while striking out seven and walking none through five innings.

"I thought Gaus was pretty good," Showalter said. "He'd probably like to have the breaking ball back. But he pitched pretty well."

Cruz broke the shutout with his one-out home run in the seventh inning.

The Cubs got the run back in the bottom of the seventh when leadoff batter Arismendy Alcantara singled home pinch-hitter Chris Valaika.

Right-handed reliever Pedro Strop, acquired by the Cubs last year with Arrieta, escaped from the eighth without a run after allowing two base runners.

After two straight days of rain factoring in delays, Friday's game went off without a hitch with partly sunny skies and high humidity.

NOTES: Friday marked a new series, but orange and black continued to be sprinkled through Wrigley Field as the Orioles visited for only the second time in history. The similarly colored San Francisco Giants just completed a series and also had plenty of fans along. "There were a lot of Giants black and orange around yesterday while I was walking around," Baltimore manager Buck Showalter said. "I just claimed them all as Orioles from a distance." ... Earlier this week, Baltimore played a three-game series at the Chicago White Sox. ... The Orioles send RHP Bud Norris (11-7, 3.69 ERA) against Cubs RHP Kyle Hendricks (5-1, 1.48 ERA) in Saturday's middle game. ... SS Starlin Castro remained away from the team for the third straight game on bereavement leave to deal with an unspecified "family emergency," the Cubs said. ... The Orioles' series is the latest in a run of four of five series against teams either first or second in their respective divisions. ... The weekend interleague series is Chicago's seventh of the season, with one to go in Toronto on Sept. 8-10. ... Cubs RHP Jake Arrieta was 20-25 in 3 1/2 seasons with the Orioles.