"His first inning was a little shaky," catcher J.T. Realmuto said. "He was leaving balls up in the zone, kind of falling behind. He fell behind [Jayson] Werth, ended up walking him. But he got himself out of the inning, and from there, he just kind of rolled."
The season has been anything but smooth for Cosart, who spent time on the disabled list in May due to vertigo. He labored when active, and was optioned to New Orleans after allowing seven runs in 1 2/3 innings at the Cubs on July 4.
In mid-July, he had a relapse with vertigo, and went on the Minor League disabled list. In early August, Cosart was examined by a specialist in Chicago, who diagnosed his condition as an inner ear disorder.
Cosart has made two starts since rejoining the club, both no-decisions but games Miami has won. He's allowed one run on nine hits with eight strikeouts in 9 2/3 innings.
"I'm just trying to show them that last year wasn't a fluke," said Cosart, who projects to be a big part of the 2016 rotation. "Obviously, what I dealt with earlier this year, it changed everything. It changed a lot of performance.
"Obviously, as a team, we're looking to put the past in the past. You can't really do anything about it. We're trying to win now. We're beating some pretty good baseball teams and playing some pretty good baseball right now."
Cosart struck out Bryce Harper to end the third and fifth innings. In the fifth, the Nationals had two on when Cosart got Harper swinging.
Cosart credits Marlins Minor League rehab coordinator Wayne Rosenthal for helping him with pitch sequence during his rehab stint in Jupiter, Fla.
"I was in my rehab, working with Wayne Rosenthal in Jupiter," Cosart said. "Working on sequencing. Working on the curveball. Throwing the curveball for strikes. I had some pretty big sequences today. The last one, to Harper, was the most important. I can say a lot of credit behind the scenes goes to Wayne down there in Jupiter."