CHICAGO -- Shortstop Starlin Castro's seventh-inning RBI single to left-center field delivered a go-ahead run as the Chicago Cubs beat the St. Louis Cardinals 2-0 on Wednesday afternoon at Wrigley Field.

Castro drove in first baseman Anthony Rizzo with none out and later scored from third on catcher Miguel Montero's sacrifice fly to right as the Cubs evened their record at 1-1.

Cubs right-hander Jake Arrieta (1-0) worked seven innings and allowed just three hits while striking out seven and walking three.

Both starting pitchers had sharp outings on a cool, cloudy afternoon and gave up just four hits combined in 6 1/2 innings until Castro's RBI single.

After Castro's hit, Cardinals right-hander Lance Lynn (0-1) was pulled in favor of left-handed reliever Kevin Siegrist. Lynn gave up two runs (one earned) on two hits, struck out nine and walked one.

Hit by a pitch to lead off the seventh, Rizzo reached second on Lynn's botched pickoff throw to set up Castro's heroics. The shortstop advanced to second on a relay throw as Rizzo scored, and Castro moved to third on left fielder Chris Coughlan's infield sacrifice.

The Cardinals threatened in the third when left fielder Matt Holliday pushed right fielder Jason Heyward from first to third base with a two-out single. But Arrieta got first baseman Matt Adams to strike out to end the inning.

Jorge Soler, a rookie right fielder, collected the Cubs' first hit of the game in the fourth with a one-out triple to center.

Rizzo walked to put runners on the corners. But Lynn struck out Castro and escaped the threat as Coughlan lofted an inning-ending fly to center.

The Cardinals threatened again in the sixth. First baseman Matt Adams reached third on shortstop Jhonny Peralta's two-out double down the left-field line. But Adams stayed put when center fielder John Jay grounded to Arrieta the final out.

NOTES: The Cardinals own the National League's best April record (215-156) since 2000 and are second in the big leagues behind the Red Sox (213-147). ... The Cubs have not announced a makeup date for Tuesday's postponed game. The Cardinals make return trips to Chicago in July and September. ... Despite Tuesday's postponement, the Cardinals stayed with their scheduled rotation, including RHP John Lackey on Friday in Cincinnati followed by RHPs Michael Wacha and Carlos Martinez on Saturday and Sunday. ... Cardinals RF Jason Heyward, an offseason acquisition from Atlanta, wears No. 22 in memory of high school teammate Andrew Wilmot, who was killed in a car accident in 2007. ... There were plenty of portable toilets -- reportedly as many as 74 -- at Wrigley Field on Wednesday after Sunday night's restroom shortage left lines snaking through the concourse and created waits as long as 45 minutes.