"It's hard to adjust. They throw hard and they have good breaking-ball pitches. You've got to be a good hitter, just to go out there and look for a good pitch to drive. Stras and Gio are pretty much wearing them down when they're in a good spot."

One night earlier, Strasburg held Boston to two runs over six innings, striking out 13.

Adam LaRoche hit a solo homer and Washington spoiled Daisuke Matsuzaka's return from reconstructive elbow surgery with its second straight win over the Red Sox.

The Nationals go for the sweep Sunday when Jordan Zimmermann faces Jon Lester.

"It's no picnic facing Zimmermann or any of our starters," manager Davey Johnson said. "That's been our strength all year, holding the opposition down."

Ian Desmond had a two-run single and Michael Morse added an RBI double during a three-run fourth for Washington.

Matsuzaka (0-1), making his first major league start since undergoing Tommy John surgery last June 10, gave up four runs and five hits over five innings, striking out eight and walking one.

"I definitely think I pitched better than I had during my rehab," Matsuzaka said through a translator. "The biggest difference today was the consistency of my velocity and the command of all my pitches."

The Red Sox have lost five of six, dropped below .500 (29-30) and are 1-4 on a six-game homestand that concludes Sunday.

Gonzalez (8-2) allowed David Ortiz's leadoff double in the second and Dustin Pedroia's infield hit in the sixth before leaving with two runners on.

Gonzalez, May's NL pitcher of the month, allowed two runs, struck out five, walked two and was helped by a pair of solid defensive plays by third baseman Ryan Zimmerman and one by second baseman Danny Espinosa.

"I felt like the team did a great job, the defensive was unbelievable, the offense came alive and the bullpen shut it down for me," Gonzalez said. "My arm slot was just going down a little bit and I couldn't find the zone after that."

Gonzalez was 5-0 with a 2.25 ERA in May.

Red Sox manager Bobby Valentine felt it was a decent first start for Matsuzaka.

"If we can build on that -- eight strikeouts in five innings -- that's pretty good,"

Jarrod Saltalamacchia had a pinch-hit, bases-loaded two-run double off reliever Michael Gonzalez in the seventh, cutting it to 4-2, but Gonzalez got the next two batters with runners on first and third.

Tyler Clippard got the final three outs for his seventh save, and second in two days.

Leading 1-0 in the fourth, Washington added three runs off Matsuzaka. Morse hit his double after Bryce Harper walked and advanced on Zimmerman's hit-and-run single through a vacant shortstop hole. Desmond followed with his single to right.

The Nationals went ahead when LaRoche homered on the first pitch of the second.

Ortiz had a leadoff double in the second, advanced on a wild pitch when Gio Gonzalez crossed up catcher Flores and hit him in the midsection with a breaking pitch. Gonzalez then got Will Middlebrooks to ground out and Darnell McDonald on a fly out.

In the sixth, Espinosa made a leaping grab of Adrian Gonzalez's liner in short right. Zimmerman had a backhand stab of Middlebrooks' second-inning grounder.

Game notes
The Red Sox designated OF Marlon Byrd before the game to make room for Matsuzaka. "Marlon came here and kind of saved the day," Valentine said. "He'll probably be with another team. I hope it's not someone on the AL East." Byrd was acquired from the Cubs on April 21 for RHP Michael Bowden and a player to be named, played in 34 games, hitting .270 with one homer and seven RBIs. ... Valentine said of Matsuzaka, "I'd like to get it over. I don't know what to expect. I've never really seen him." ... The Nationals' team bus was stuck in traffic and took nearly 90 minutes to get to the park. Manager Davey Johnson did not talk to the media before the game, sending bench coach Randy Knorr to take his place because of the late arrival. ... Thirty-three cancer survivors cycled around the warning track before the game, kicking off the 33rd annual Pan Mass Challenge, a two-day bike-a-thon that will be held in August to raise money for cancer research and patient care. Player wives Tiffany Ortiz and Holly Beckett are expected to join the Red Sox team of riders.