Jordan Zimmermann was dominant against the Phillies on Tuesday. (Greg Fiume/Getty Images)

In his five starts in May, Nationals starter Jordan Zimmermann allowed 15 earned runs over 26 2/3 innings, good for a 5.06 ERA. The right-hander, a model of consistency in 2013, wasn’t much of that last month. But in his first start of June, Zimmermann returned to form.

He allowed only five hits, walked one and struck out four over eight scoreless innings Tuesday in a 7-0 win over the Phillies. He threw 102 pitches in his longest, start of the season.

“It was big,” he said. “May was a pretty rough month for me. Hopefully June has better things to come. It was good to eight. I wanted to go nine but eight will be good enough.”

After a rough stretch last month, Zimmermann pitched like himself Tuesday thanks to better command and a better feel for his slider, the pitch he pairs with his fastball to neutralize right-handed batters. In past starts, the pitch was “a little flat.” Against the Phillies, it was sharper and, because of the humidity, he said he was able to have a better feel for the pitch in his hands.

“I was throwing it and it was going where I wanted it to,” he said. “Overall, it was good.”

“He threw a lot of sliders today for strikes,” Manager Matt Williams added. “He had not really found it. He threw some good ones but it hasn’t been consistent. [Tuesday] it was consistent. He worked change-ups, and sliders to the right-handers and was able to throw it for strikes, which was good.”

In between his rough starts and now, Zimmermann said nothing changed. He simply did a better job of hitting his spots. In past starts, he missed his location by a small fraction, enough to get hit hard. Tuesday was a big improvement. And when he needed to waste a pitch while ahead on opposing hitters, he did a better job of that than in past starts.

“When I wanted to throw a ball, I was throwing a ball and not leaving it over the middle,” he said. “We had a really good game plan and [catcher Wilson Ramos] and I were on the same page. It was one of those nights it was fun to be out there and everything working.”

Zimmermann encountered his only jam in the eighth inning when he gave up three straight two-out singles, two of them on first pitches. But he escaped the inning by inducing a ground out from Marlon Byrd. It was the first time in 12 starts that Zimmermann pitched into the eighth inning. Last season, he did that 10 times.

“It was one of those nights it was fun to be out there and everything working,” he said.