ST. LOUIS -- Informed that Washington had just won its first series in St. Louis since 2007, left fielder Jayson Werth sounded incredulous.

"That's crazy," he said. "I don't have anything else for you on that."

Werth used his bat to do most of the rest of his commentary, capping a four-run first inning with a three-run homer as the Nationals topped the sloppy Cardinals 6-1 on Saturday in Busch Stadium.

Making his first start since April 20, Joe Ross worked six solid innings to improve to 3-0 as Washington won for just the ninth time in 35 games in St. Louis since the franchise moved from Montreal before the 2005 season.

"They're always tough here," said Nationals manager Dusty Baker, who has endured his share of losses in the visitors' dugout as the former manager of the Cincinnati Reds. "They're tough anywhere."

The Cardinals weren't so tough in this one, tripping all over themselves throughout the day with a combination of bad at-bats, poor defense and a lack of control from their pitchers.

Jaime Garcia (1-2) struggled with fastball command in the first, consistently falling behind in counts and extending the inning with a two-out walk to Ryan Zimmerman. Washington pounced with an RBI single by Daniel Murphy to set the stage for Werth.

After gaining the count advantage, Werth took a strike and then lashed a 2-1 changeup into the left field seats for his fourth homer of the year. While Werth is batting only .211, he does have eight extra-base hits and 13 RBI.

"I was beginning to wonder if I was ever going to catch a break," Werth said. "You know, that was a pretty good changeup he threw me, a tough one to get in the air. It was good to get those runs in. Obviously, that helps give you confidence."

Staked to a big cushion before tossing his first pitch, Ross made it stick, scattering six hits in his stint and allowing St. Louis' only run with two walks and four strikeouts. After retiring 11 straight hitters following a leadoff double by Jeremy Hazelbaker, Ross maneuvered in and out of trouble the last 2 1/3 innings.

Ross has allowed only two runs in his first four starts, covering 22 2/3 innings.

"It's not surprising to me, because from what I heard when I took this job, his stuff was as good as anyone on this staff," Baker said of Ross.

The Cardinals (12-12) loaded the bases with one out in the fifth for their 2-3 hitters. Matt Carpenter lined a sacrifice fly to center that scored Ruben Tejada, but Matt Holliday bounced the first pitch he saw to shortstop Danny Espinosa for an inning-ending forceout.

The Cardinals actually outhit the Nationals 8-6 but were their worst enemy. They made three errors, two by Hazelbaker in center that figured into both Washington rallies, issued five walks and hit two batters.

Garcia refused to blame the defense, which leads the National League with 24 errors.

"Those guys have made great plays behind me in the past and they're working on (defense) every day," he said. "I walk batters, too. Bottom line is I could have been better in the first inning. I can't put us four runs down."

Two walks, a hit batter, a fielding gaffe by Hazelbaker on a Murphy single and Werth's sacrifice fly led to the Nationals' final runs in the eighth.

Three relievers finished up Ross' win for Washington, which wrapped up April with a 16-7 mark for Baker, its first-year manager.

"It was a good month, but it's only one month," he said. "Now we go out here tomorrow and start a new month."

One of the few bright spots for the Cardinals occurred when shortstop Aledmys Diaz singled in the ninth for his 30th hit of April, making him the second rookie in team history to accomplish that feat. Albert Pujols did it in 2001.

NOTES: St. Louis third base coach Jose Oquendo will need knee replacement surgery next month, meaning he won't be able to join the coaching staff this season. Oquendo has been part of the team's coaching staff since 1999. ... Washington's 16-7 start is its best since the franchise moved from Montreal after the 2004 season. ... Cardinals SS Jhonny Peralta (left thumb) has started light fielding drills and is hopeful of going out on a rehab assignment in three weeks. Peralta was injured in spring training.