WASHINGTON (AP) Stephen Strasburg and the Washington Nationals put a perfect finish on another rough day for the sputtering Chicago Cubs.

Strasburg struck out 13 in seven innings, Bryce Harper had two doubles and two RBIs, and the Nationals beat the Cubs 8-4 on Wednesday night.

Anthony Rendon and Matt Wieters hit back-to-back homers against John Lackey (5-9) during Washington's four-run second inning. After the Cubs pulled within three at 6-3, Daniel Murphy went deep in the fifth.

The Cubs lost for the fourth time in six games to drop back to .500 at 39-39. They cut veteran catcher Miguel Montero after he criticized pitcher Jake Arrieta for his role in the Nationals' seven steals Tuesday night, and then reigning NL MVP Kris Bryant departed with a right ankle sprain.

''Things happen. You have to fix them when things happen,'' Cubs manager Joe Maddon said. ''You don't cry. Of course suboptimal, no question.''

Bryant awkwardly clipped third base while catching a foul pop off the bat of Wieters in the sixth. He walked around gingerly before being helped off the field. An X-ray was negative and Bryant is expected to miss at least the next two games, according to Maddon.

''We have a game to win tomorrow,'' Maddon said. ''(Bryant) will not be starting, obviously, so we'll try to figure it out in another way.''

Strasburg (9-2) allowed three runs, two earned, and four hits before leaving with back spasms. He improved to 6-1 in his last nine starts.

''He had it going on tonight,'' Nationals manager Dusty Baker said. ''You could just sort of tell when he left last night that he was going to be ready. Today, he had that kind of look in his eyes.''

Ryan Zimmerman drove in two runs for the NL East-leading Nationals, who have won two in a row over the World Series champions after dropping Monday's series opener.

Willison Contreras and Anthony Rizzo homered for Chicago. Lackey allowed a season-high eight runs and nine hits over 5 1/3 innings.

Strasburg rebounded after allowing five earned runs in five innings during a no-decision against Cincinnati on Friday. He retired nine of his first 10 batters and struck out the side in the second and third innings.

After Contreras's two-run homer in the fourth and a Chicago run in the fifth, Strasburg set down his final eight batters.

Strasburg initially felt his back spasm while sitting on the bench in the fourth inning.

''The first couple throws warming up going back out there, you feel it a little bit,'' he said. ''Just tried to mentally not let it affect me. I think it kind of helped just slow everything down a little bit, especially after a couple runs scored there in the middle innings.''

Rizzo hit his team-leading 18th home run against Enny Romero in the eighth.

Harper doubled and scored in the first inning on Zimmerman's base hit. He added a bases-loaded walk in the second and an RBI double in the sixth off Brian Duensing.

TRAINER'S ROOM

Nationals: RHP Koda Glover said an MRI on his shoulder revealed severe inflammation of the rotator cuff, and he is waiting for it to go away. ''I'm still a little bit of a ways from throwing,'' he said. Glover, who is 0-1 with a 5.12 ERA and eight saves in 23 games, went on the disabled list June 11 with what the team described as lower back stiffness.

Cubs: SS Addison Russell (shoulder) was out of the starting lineup for a third game in a row, but Maddon said there's a chance he could play in Thursday's series finale. ... 2B Ben Zobrist (wrist) starts a rehab assignment Thursday with Double-A Tennessee. He landed on the DL on June 16.

WORTH NOTING

Chicago recalled catcher Victor Caratini from Triple-A Iowa to replace Montero. Caratini hit .343 with eight home runs and 54 RBI in 68 games for Iowa this season.

SUBSTITUTE COACH

Nationals first base coach Davey Lopes left the team before the game due to a family emergency. Assistant coach Jacque Jones replaced him.

HOME RUN PROBLEMS

Washington's three homers ran Lackey's season total to 24 in 16 starts. The right-hander gave up 23 in 29 starts last season.

''The second inning was pretty much the game,'' Lackey said. ''I didn't make enough good pitches.''

UP NEXT

Cubs: LHP Jon Lester (5-4, 3.83 ERA) is 2-3 with a 5.49 ERA in seven road starts this season.

Nationals: RHP Joe Ross (4-3, 5.40 ERA), who has lost both of his career starts against the Cubs, gets the ball as Washington wraps up a seven-game homestand.

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