Jayson Werth charges to third on a first-inning double by Danile Murphy. Werth was held, but scored when Anthony Rendon hit a three-run home run a few moments later, part of a four-run Nationals’ first inning. (Jonathan Newton/The Washington Post)

After the Washington Nationals beat the Seattle Mariners, 5-1, on Wednesday evening, Tanner Roark sat at his locker, red game cap on, red “202” shirt paired with it, just sitting as the rest of his teammates hurried home.

Pitching coach Mike Maddux, dressed and ready to go, stopped by on his way out and made a “Welcome Back, Kotter” reference. Roark didn’t have any idea what his enigmatic coach was talking about, though he may have understood the gist.

During seven innings in which he allowed one run, kept his pitch count down and used his trademark two-seamer as well as he has all season, the old, familiar Tanner Roark seemed to find his way back to the Nationals Park mound.

“I felt like the two-seamer was moving, so that’s a positive itself,” Roark said. “That’s my biggest thing, my two-seamer working. I was hitting my spots.”

After he threw 114 pitches in five grueling innings against the Pirates last week, Roark admitted the game was “testing him.” The pitcher known for pummeling hitters into quick submission suddenly ranked as one of the most inefficient starters in the game — particularly with two strikes, when he seemed unable to bury hitters but prone to lengthy battles.

Theories varied as to why. Roark mused that he might have been trying so hard to pinpoint in those situations that pitches went elsewhere. His catcher, Matt Wieters, wondered whether a few too many of his two-strike pitches were “noncompetitive” — not close enough to entice a swing. Both agreed that inconsistencies with the location and movement on his two-seam fastball were not helping.

Between starts, he and Maddux chatted in the outfield while shagging balls during batting practice. Among the conclusions reached by the duo was that Roark was gripping his two-seamer too tightly — effectively throttling the life out of it.

“You’ve got to treat it like an egg. Can’t break the egg,” Roark said. “That’s what I was telling myself.”

That unlikely determination seemed to pay off Wednesday as Roark stiff-armed inefficiency. He settled in after a slow start, getting two strikes on 14 hitters in those seven innings and retiring 13 of them. He struck out eight and averaged one two-strike pitch per out through the last six innings. In other words, when he got ahead, he got outs, and he threw a manageable 102 pitches.

“He threw another competitive pitch with two strikes when he got there. He didn’t get to where it was 1-2, 2-2, 3-2,” Wieters said. “He made them put a ball in play 0-2 or 1-2.”

Relying heavily on that two-seamer, Roark mowed through the Mariners by getting weak contact early and groundballs when he needed him — exactly the recipe on which the right-hander relied last season. He scattered eight hits and did not walk a batter while matching his longest outing of the season.

“Sometimes you’re trying too hard to execute it, you cease being natural and throwing the ball where you want to throw it,” Manager Dusty Baker said. “So tonight was more like Tanner.”

The Nationals’ offense backed Roark with four runs in the first, punishing soft-tossing rookie Sam Gaviglio with an outburst capped by Anthony Rendon’s third home run in two games. But the Nationals (28-17) could add only one more run, meaning Roark’s steadiness mattered a great deal more than it looked like it would during the Nationals’ initial offensive.

That the Nationals could not add to their early output also meant they handed a sizable but not at all comfortable four-run lead to their bullpen. Enny Romero started the eighth, got two outs and allowed a hit. Shawn Kelley got his man to finish it. Koda Glover pitched the ninth.

No one officially named Glover the Nationals’ closer, but after he earned the save Sunday in Atlanta, Baker suggested it was his job to lose. On Wednesday, he threw a 1-2-3 ninth, mixing a 98-mph fastball with a slider and a recently honed curve.

“He had said that’s the job he wanted,” Baker said, “and so it’s his now.”

No antidote has been found that can help a disheveled bullpen coalesce. No elixir exists that can slump-proof a lineup. But a daily dose of strong starting pitching can quell even the most troubling baseball symptoms.

By the time Roark delivered seven innings of one-run ball, Nationals starters had allowed three runs in their past 22 innings. The Nationals had won all three of those games. Their bullpen did not allow a run in any of them. The Nationals had the biggest division lead in baseball despite Roark’s struggles. On Wednesday, they welcomed him back.