Nationals 10, Brewers 5: Bryce Harper homered in his first at-bat after coming off the disabled list and Jordan Zimmermann became baseball's second 12-game winner as host Washington won the opener of a four-game series.

Harper, who was sidelined for 31 games with bursitis in his left knee, drove the second pitch he saw from Milwaukee starter Yovani Gallardo the opposite way for his 13th home run of the season. Jayson Werth was 2-for-5 with five RBIs to pace the Nationals' attack.

Zimmermann (12-3) gave up four runs and nine hits in six innings to improve to 3-0 against the Brewers and pull even with Detroit's Max Scherzer for the most wins in the majors. He also helped his own cause by going 3-for-3 with two runs scored.

Harper's blast set the tone against Gallardo (6-8), who was shelled for eight runs in just three innings. Zimmermann doubled to start the third and scored on Werth's two-run double as the Nationals raced to an 8-0 lead after four frames.

Rickie Weeks and Juan Francisco hit back-to-back homers in the sixth inning as Milwaukee crawled to within four at 8-4, and Aramis Ramirez's RBI double in the seventh made it a three-run game. Werth, who also had a two-run single in the fourth, had an RBI groundout in a two-run eighth to help send the Brewers to their sixth straight loss.

GAME NOTEBOOK: Washington LHP Ross Detwiler was cleared to start Wednesday against Milwaukee after having no pain following a throwing session. Detwiler had a stiff lower back after facing the New York Mets on Friday. ... Gallardo has a 7.40 ERA in five career starts at Nationals Park. ... Zimmermann entered 3-for-32 on the year.