Anthony Rizzo hit his first homer with the Cubs, a two-run go-ahead shot in the fifth inning, and Chicago beat the Houston Astros 3-2 Saturday for its fourth win in five games.

Matt Garza (4-6) struggled but got the victory by working 5 1-3 innings. Five Cubs relievers combined to allow one hit and no runs over the final 3 2-3 innings with Carlos Marmol pitching the ninth for his seventh save in nine chances.

Astros lefty J.A. Happ (6-8) allowed five hits, four walks and three runs in six innings. But the former Northwestern University hurler is winless in his past 11 road decisions dating to May 3, 2011.

Veteran Astros first baseman Carlos Lee, the subject of trade rumors involving the Dodgers, went 0 for 4.

Rizzo's long and high blast to right field scored Starlin Castro for a 3-2 lead. Moments earlier, Castro had hit a two-out RBI single for Chicago's first run.

Rizzo, whose arrival in Chicago on Tuesday was met with great buzz after an impressive stint in Triple-A, also made a nice defensive play in the third to cut down a Houston run. The homer was the second of his major league career. He had one last season with San Diego.

Garza labored on the 92-degree afternoon but was backed by three double plays and some overly aggressive base running by the Astros. He gave up two runs and nine hits in 5 1-3 innings and threw 104 pitches with three walks. Scott Maine relieved him in the sixth and gave up a single to Jason Castro, but Cubs left fielder Alfonso Soriano made a strong throw to get Chris Johnson trying to make third on the hit.

A leadoff single by J.D. Martinez, double by Scott Moore and single by Jordan Schafer gave the Astros a 1-0 lead in the third. But a big inning was averted when Rizzo fielded Jed Lowrie's grounder and made a strong throw to the plate to easily nail Moore.

Martinez hit a two-out RBI single in the fourth, right after the Cubs had turned a 5-3 double play with two runners on. But he was caught off second after initially heading for third on Moore's single and was tagged out to end the inning.

Astros shortstop Lowrie saved a run in the fourth with a great stop on Darwin Barney's hard two-out grounder and then shoveled it backhanded to second baseman Moore for the out.

Notes: Astros 2B Jose Altuve (right hamstring) ran sprints on Saturday and there is a chance he could play Sunday after missing six straight games. ... Cubs 3B Ian Stewart could be headed for surgery after his injured left wrist has not responded to treatment. .... RHP Ryan Dempster (DL with a lat injury) is slated to throw a bullpen session Monday in Atlanta. ... Astros manager Brad Mills said he's hoping RHP Wilton Lopez (right elbow sprain) will be ready to return after the All-Star break. Lopez is scheduled to throw a bullpen session during the team's next stop in Pittsburgh.