Stephen Strasburg dominated the Philadelphia Phillies on Thursday to fuel the growing sentiment around Washington that he, and not Max Scherzer, should be the Nationals’ starter in Tuesday’s National League wild-card game.

Strasburg baffled the Phillies, facing two more than the minimum in his six innings, and his only mistake was a solo homer in the fourth. The 31-year-old right-hander otherwise sailed through the outing, and his last start of the regular season ultimately gave the Nationals enough leeway so that, when the bullpen later struggled, they still emerged with a 6-3 win. When asked what he expected next week, Strasburg demurred.

“I’m just here to help the ballclub in any way possible,” he said. “It’s going to take all 25 of us.”

The victory was the Nationals’ 90th of the season, and it finished the first five-game series sweep in team history. It nudged them ahead of the Phillies in the teams’ all-time series, 140-139, and gave them 14 wins in 19 games against Philadelphia this year. Most importantly, it maintained their one-game lead for the top NL wild-card spot over the Milwaukee Brewers, who beat the Cincinnati Reds for their 18th victory in their past 20 games.

The Brewers’ surge has pulled them within a game of the idle St. Louis Cardinals for the NL Central lead and has further muddled who the Nationals might face in the wild-card game. Each team has one three-game series left: The Cardinals host the Chicago Cubs, the Brewers visit the Colorado Rockies, and the Nationals host the Cleveland Indians, who are clawing for a spot in the American League wild-card race. Manager Dave Martinez said Nationals decision-makers will meet this weekend to determine the playoff roster, though they are preparing for two teams now, instead of the expected one.

“I know we got scouts flying all over God’s green earth to watch different teams play,” he said.

Strasburg did his part to keep the Nationals in a favorable spot heading into the final weekend. He had a stellar season, bouncing back from a dissatisfying 2018 to finish with a 3.32 ERA over 209 innings. He and Martinez credited his dependability on a change to his offseason workouts and routine between starts. Strasburg punctuated the resurgence by striking out 10 Thursday — including Bryce Harper three times — to set a new career high of 251 in a season.

Strasburg fanned Harper on a different pitch each time, using a curveball, fastball and change-up. Catcher Yan Gomes emphasized Strasburg’s ability to throw any of his pitches for strikes at any time, and Strasburg singled out the development of one pitch from the start of his career in 2010.

“My change-up has really evolved over the years,” he said. “When I first started my pro career, it was a pitch I threw once or twice a game. Over the years it’s turned into a weapon.”

The argument for starting Strasburg begins with the fact Scherzer hasn’t been the same since he returned from the injured list in late August. He has made four starts at full effort and, though his stuff has looked the part, he has posted a 4.94 ERA. His track record in the postseason, a 3.73 ERA in 16 appearances, pales against Strasburg’s one earned run over 19 innings across three starts.

Strasburg, meanwhile, capped the most dominant and durable season of his career with a 33rd start that could serve as a fine final audition. He mostly cruised, erasing the two singles he allowed by getting the next hitter to bounce into a double play. His only real hiccup was a curveball that caught too much of the plate in the fourth that César Hernández hooked just fair down the right field line. Strasburg rebounded against the next batter, Harper, showing what he had left in the tank. He reached back for a 96-mph fastball, his hardest pitch of the afternoon, and blew it by Harper for strike three. Gomes described catching Strasburg as “fun.”

“It’s just a matter of getting on the same page and communicating,” Gomes added. “There’s some times when all his pitches are working [and] you don’t feel like any of the fingers are wrong fingers.”

The closest Strasburg came to danger the rest of the afternoon was a leadoff double by Andrew Knapp in the sixth. He pitched around it by striking out the next three hitters, finishing with Harper again. Strasburg departed at 92 pitches and, though it looked like a nod toward conservation for the wild-card game, Martinez said it was because the pitcher felt a slight cramp in his right hamstring. The manager said the move was precautionary and that the pitcher is “all good” for the playoffs.

Still, Martinez intimated this week he expects Scherzer to start Tuesday. He said, “If you look at the schedule right now, that’s Max’s day.” But Scherzer is lined up to start Sunday, which still could happen if the Nationals need to win to secure home-field advantage in the wild-card game, and Strasburg would be on regular rest for Tuesday. Martinez couched his comments before Thursday’s game and said he would likely decide Saturday who will get the ball for the one-game playoff.

The seventh inning arrived Thursday, and Strasburg stayed in the dugout. One of the most successful seasons of his career was over. He was standing in the dugout when teammate Gerardo Parra approached. The outfielder stretched out his arms, and Strasburg, famously withdrawn, didn’t react. Parra advanced anyway, wrapping his arms around the pitcher, and Victor Robles and Aníbal Sánchez followed. Strasburg couldn’t move in the middle of the group hug, but he did crack a grin.

“They cornered me,” he said, smiling. “I had nowhere to go, so I just had to embrace it.”

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