WASHINGTON -- Nationals manager Dusty Baker was concerned. His team had a 3-1 lead, but in the sixth inning Jedd Gyorko got a base hit when his grounder bounced off the third-base bag.

In the seventh inning, Matt Holliday reached on an infield single as he beat out a high chopper to shortstop and the Cardinals eventually cut the lead to 3-2.

But small ball was no match for long ball, as Jayson Werth hit a pinch-hit grand slam in the seventh and Wilson Ramos hit a two-run shot in the eighth as Nationals beat the St. Louis Cardinals 10-2 on Sunday, earning a split of the four-game series.

Werth had the day off and worked on his swing indoor cages during the game before facing Dean Kiekhefer in the seventh.

"I saw the opportunity to hit off a lefty," said Werth, who hit his sixth career grand slam and fourth career pinch-hit homer. "I was able to get ready for the at-bat. He left a heater over the middle."

Said Kiekhefer: "I threw him a first-pitch changeup and fell behind. I was trying to go with a fastball in, run him back over with a sinker and get a groundball in that situation. Unfortunately I left it down the middle for him, and he put a good swing on him."

There were plenty of heroes for the Nationals, who begin a series on Monday in Philadelphia.

Stephen Strasburg remained unbeaten as he allowed one run in six innings and Ramos had three hits and four RBIs.

"He is certainly earning his money," Baker said of Strasburg, who signed a contract extension earlier this season. "He has the stuff to be a big-time winner."

Strasburg (9-0), now tied for the league lead in wins, gave up six hits and two walks with four strikeouts and lowered his ERA to 2.69. Washington has won every game he has started this year and the last 15 overall. Oliver Perez, Blake Treinen, Felipe Rivero, Shawn Kelley and Jonathan Papelbon combined to get the last nine outs for the Nationals.

"He has been great," Werth said of Strasburg. "I really noticed a change in him in spring training. He looked like he was in real good shape. So far so good. The contract has helped. It has got to feel good" about signing a long-term deal with the team that drafted him.

Losing pitcher Michael Wacha (2-6) gave up three runs on four hits in six innings. Wacha didn't allow a hit in the first three innings before Washington scored three runs in the fourth.

"We've been beat up. I had to stay away from (Kevin) Siegrist and (Seung Hwan) Oh today, and we needed a couple other guys to try and come through for us, and we couldn't hold them back late," Cardinals manager Mike Matheny said of his bullpen.

Wacha was encouraged his outing.

"Definitely a step forward. I felt like I was locating a lot better down in the zone and staying down in the zone. It's a good start to build off of. Just have to continue between starts getting better," he said.

Bryce Harper had an RBI single in the fourth to tie the game at 1-1. His hit scored Michael A. Taylor, who led off the frame with a double. Ryan Zimmerman had a double with one out and Ramos drove in Taylor and Zimmerman with a two-out single to make it 3-1.

"It was good to get (those runs) when we did," Baker said. "It was nice for us to have a few crooked numbers. I am very encouraged (with the offense). I think that this is a hot weather team."

Matt Adams of St. Louis had a sacrifice fly in the seventh off Rivero to cut the margin to 3-2. But Anthony Rendon, who also had two hits, then led off the last of the seventh with a homer on the first pitch from Jonathan Broxton to make it 4-2, and Werth came through later in the frame.

The Cardinals took a 1-0 lead in the fourth on a solo homer by Brandon Moss (two hits), who went deep for the ninth time this year.

Strasburg got out of danger in the sixth when a single by Gyorko (two hits) bounced off the third base bag and bounced over Rendon, the third baseman. That put runners on first and second with two outs, but Strasburg retired Eric Fryer on a popup to end the inning.

Matt Holliday had three hits for the Cardinals (26-25), who start a series on Monday in Milwaukee.

NOTES: Washington RF Bryce Harper received the Players Choice Award as a 2015 National League Outstanding Player in a pre-game ceremony. ... Cardinals 1B Matt Adams (.327, 23 RBIs) was in the starting lineup for the first time since Thursday, when he left in the fifth inning with back problems. He did not play Friday, and then Saturday had a two-run, pinch-hit double in a 9-4 win. ... Washington 2B Daniel Murphy began the day with 41 hits in May, the most in franchise history (2005 to present) in one month. The old mark belonged to OF Denard Span, who had 40 in August 2014. ... Washington RHP Tanner Roark (3-4, 3.71 ERA) will start on Monday at Philadelphia against Phillies RHP Jeremy Hellickson (4-3, 3.97 ERA). ... The Cardinals head to Milwaukee and will face the Brewers and RHP Junior Guerra (3-0, 3.30) on Monday. RHP Carlos Martinez (4-5, 4.25 ERA) will start for St. Louis and try to snap a five-game losing skid. ... The Nationals were 14-0 in the last 14 starts for RHP Stephen Strasburg, the Sunday starter, dating back to Sept. 15, 2015.