Cubs 4, Orioles 1: Jake Arrieta burned his former team by scattering four hits over seven innings and Luis Valbuena and rookie Javier Baez each belted a solo homer as host Chicago won the opener of a three-game interleague series.Logan Watkins and Arismendy Alcantara each added an RBI single as the Cubs improved to 2-2 on their six-game homestand. Valbuena finished with two hits and has 10 in his last six contests.Nelson Cruz belted his major league-leading and career-high 34th homer for Baltimore, which had won four straight and 12 of of its previous 16 contests. The Orioles saw their lead in the American League East dip to 8 1/2 games.Arrieta (7-4), who began his career in Baltimore before being shuffled to Chicago last season, retired his first 13 batters en route to recording just his second win in nine turns. The 28-year-old's lone misstep came in the seventh on Cruz's third homer in four games, but allowed just that one run before Hector Rondon retired the side in the ninth for his 20th save.Valbuena opened the scoring with two out in the fourth inning by depositing an 0-2 fastball from Kevin Gausman (7-5) over the wall in right-center field for his 12th homer - and second in three games. Watkins, who was recalled from Triple-A Iowa on Thursday, singled to center later in the frame before Baez extended the lead with two out in the fifth by sending a 3-2 forkball onto Waveland Avenue. GAME NOTEBOOK: Chicago RF Ryan Sweeney threw out Baltimore's Chris Davis at the plate to end the fifth inning and preserve his team's 2-0 lead. Orioles manager Buck Showalter argued that Cubs C John Baker had blocked the plate, but the umpires reviewed the play and upheld the call. ... Gausman permitted three runs on six hits in five innings. ... Baltimore 3B Manny Machado, who was eligible to come off the 15-day disabled list Wednesday, will reportedly undergo season-ending surgery on his right knee within the next week.