NEW YORK -- Toby and Jodi Roark were in the midst of a 12-hour drive from Wilmington, Ill., to Washington, D.C., to watch their son Tanner pitch in the Nationals' home opener. Then they got a call from their daughter-in-law, telling them he wouldn't be starting Friday.

In the clubhouse at Citi Field, Tanner's phone beeped.

"My mom is texting me, 'What's happening?'" Tanner remembered. "They were bummed out."

Jordan Zimmermann had a fever and was vomiting, so Roark started Thursday's series finale against the New York Mets on just three hours' notice.

Nationals first-year manager Matt Williams said Zimmerman may start Friday's home opener after he was given fluids and sent home ahead of the team.

"We don't want to send him out there with him being really sick, so we'll see how that goes in the morning," Williams said.

After a shaky first inning, Roark recovered and the Nationals rallied for an 8-2 victory and an opening three-game sweep.

"I just go with the flow," the 27-year-old right-hander said. "Whatever they tell me to do, it's what I'm here for."

Ryan Zimmerman tied his career high with four hits, including three that led off innings. His second-inning home run off Zack Wheeler (0-1) started the Nationals' comeback from a 2-0 deficit.

Washington's leadoff batter reached in the first seven innings, and the Nationals rallied to win for the third time in the series. While Washington opened 3-0 for the second straight season, the Mets fell to 0-3 for the first time since 2005. They had not lost their first three home games since 1997.

"They're proud of the way they've played so far and so am I," Williams said. "Just the way they're grinding."

Roark (1-0) made his major league debut on Aug. 7 last season and went 7-1 with a 1.51 ERA in five starts and nine relief appearances. He got just two swings and misses in the first four innings and fell behind 2-0 in a 30-pitch first but wound up allowing just the two runs and six hits in six innings with three walks and five strikeouts -- including his final four batters.

"That's what Tanner's done since basically we called him up last year," Zimmerman said. "When it's his turn to pitch, he goes out there and challenges the hitter. He throws a lot of strikes and works quick."

Roark allowed an RBI double in the first to Curtis Granderson, who had been 0 for 9 with the Mets, and Juan Lagares' sacrifice fly. Then he started making adjustments.

"I was letting the ball go and not trying to pinpoint and try to nibble as much," he said.

Wheeler gave up three runs and seven hits in six innings, trying to work out of trouble for much of the afternoon before a small crowd of 20,561, a couple hundred above Citi Field's record low.

Washington went ahead 3-2 in the fifth when Denard Span hit an RBI single to right, advanced as Granderson heaved a two-hop throw home and scored on Jayson Werth's two-out single. The Nationals broke open the game with a four-run seventh against relievers Scott Rice and Jeurys Familia that included a two-run single by Adam LaRoche off the glove of first baseman Lucas Duda.

"I assure you, we're better than what you've seen the last three days," Mets manager Terry Collins said.

Soon after that, thoughts turned to the home opener against Atlanta. Roark said his parents and in-laws still plan to be in the stands at Nationals Park on Friday and Saturday.

"They'll still get there, spend time together, so that's good," he said. "First time in D.C., so that will be fun."

Game notes
Washington pitchers struck out 39 in the series, third-most in any team's opening three games since 1914, according to STATS. The only teams with more were Texas last year (43) and Cleveland in 1966 (42). ... Mets 2B Daniel Murphy returned from paternity leave and had a throwing error and a fielding error in his season debut. ... Homeland Security Secretary Jeh Johnson presented the Rick Rescorla National Award for Resilience to the New York Mets, Walgreens and Monsignor John Brown, then bounced the ceremonial first pitch. ... Werth was 6 for 13 in the series and Zimmerman 6 for 14.