Nationalsbatter Wilson Ramos walks off between Astros catcher Humberto Quintero (55) and home plate umpire Jeff Nelson. (Pat Sullivan/AP)

Jordan Zimmermann stood on the middle of the diamond minutes after he had started his workday Tuesday night. His manager, his pitching coach and a trainer inspected him. Zimmermann had taken a line drive off his left shin, and he did the funniest thing: He was laughing. The Washington Nationals’ starter threw one pitch and then waved off the three men standing behind. In college, the guy pitched a playoff game with his jaw wired shut.

“It hurt,” he said. “But I wasn’t going to come out.”

In the innings after Zimmermann added another piece of evidence to the accepted belief that nothing rattles him on the mound, another funny thing happened: The Houston Astros beat him around. In the Nationals’ 7-6 loss before 32,418 at Minute Maid Park, Zimmermann allowed six earned runs in five innings — the highest run total and shortest start of his season.

With about seven starts remaining before he reaches his 160-inning limit for the season, Zimmermann allowed six runs on seven hits with no walks. His start seemed worse than it was because of the high standard he had set over the course of his first full season back from Tommy John surgery. Before Tuesday, his 2.16 ERA since May 1 ranked best in the National League.

“I just didn’t have a good feel or touch for anything,” Zimmermann said. “My slider was pretty terrible tonight. I had a rough time locating the fastball. When you have nights like that, you’re going to get hit around. It’s a shame that the offense puts up six runs. I feel like I didn’t do my part.”

Zimmermann had become accustomed to either overcoming or succumbing to the Nationals’ offense. It had averaged 3.1 runs in games he started. But Tuesday night it finally supported him. Michael Morse reached base five times — a two-run home run, two doubles, a walk and a hit by pitch — and Jerry Hairston, playing for the first time in three weeks, roped a double and a two-run home run.

But the Nationals also squandered chances to overtake the Astros and win for the second straight night against the team with baseball’s worst record. In the ninth, after Astros closer Mark Melancon hit Morse with a pitch and walked Jayson Werth on a 3-2 fastball, Wilson Ramos flailed at a 1-2 breaking ball in the dirt to end the game.

Ramos had also left the bases loaded in the first inning with a popup. The Nationals stranded nine runners, six on either second or third, and went 2 for 10 with runners in scoring position. In the eighth, they spoiled a rally before it even started. Hairston lined a leadoff single off the base of the wall, but he, the tying run, was thrown out at second by trying to turn it into a double. The ball caromed off the shallow wall right to Carlos Lee, who is not know for his defensive aptitude, and he barehanded the ball and fired a bullet to second. Hairston still couldn’t believe it afterward.

“I made a judgment call,” Hairtson said. “Everything had to go perfect for him to throw me out. And it did. Even then, he barely got me. Some guys, you test. There’s other guys you don’t. I’ve known Carlos a long time, and he knows I’m going to test him. He made a great play.”

The Nationals could usually count on a win scoring six runs behind Zimmermann, but not Tuesday. Zimmermann’s first blemish came in the second, and in unfamiliar fashion. Zimmermann’s success has been based largely on not walking hitters and keeping the ball in the park. He entered Tuesday night having allowed only four home runs, and his 0.31 homers per nine innings ranked fifth lowest in the major leagues. With a man on first and two outs, though, Clint Barmes smoked a 93-mph fastball into the seats in left field, giving the Astros a 2-0 lead. Zimmermann threw a fastball inside, and “I didn’t get it in enough."

Afterward, Manager Davey Johnson zeroed in on a different pitch. In the fourth, Barmes came to the plate in a 2-2 game with men on second and third and one out. Zimmermann quickly got ahead of him with two strikes.

At that point, Johnson wanted Zimmermann, with light-hitting catcher Humberto Quintero up next, to give Barmes nothing to hit. Zimmermann threw two balls, but then a mistake: a slider down the middle. Barmes ripped a single, opening the floodgates for a five-hit, four-run inning. Johnson called the pitch “the thing that bothered me the most out of that whole ballgame.”

“If he gets ahead of the guy, I don’t expect him to make bad pitches,” Johnson said. “The hitter’s got to hit a pitch off the plate, a nasty pitch. He hung a slider right down the middle. It was flat. . . . I thought he battled, and maybe he didn’t have his best stuff. When you got two strikes on the batter, he basically threw him a cookie.”

Said Zimmermann: “I probably could have thrown something in the dirt. But it’s one of those nights when you don’t have a feel for your slider, your curveball. I didn’t have anything. I didn’t know where it was going to go.”

Still, the Nationals responded in the bottom half of the inning. Ramos led off with a bloop single. Two batters later, Hairston came to the plate. Playing in his first game since June 29, when a fastball him in the left wrist and broke a bone, Hairston had already hit a double. Now, he knocked Astros starter J.A. Happ out of the game with a laser over the left field scoreboard. Alex Cora, pinch-hitting for Zimmermann, walked, stole second and scored on Ian Desmond’s two-out single, making it 6-5.

In the sixth, right-handed reliever Todd Coffey couldn’t keep it a one-run game, allowing a single, a walk and another single, all with two outs, to give the Astros their seventh run. When Morse doubled to lead off the seventh and eventually scored, he brought the Nationals within one rather than tying the score.