Nationals pitcher Stephen Strasburg struck out 10 Phillies, yielded three hits and never allowed a runner past third base. (Toni L. Sandys/The Washington Post)

Jose Lobaton extended fingers toward the dirt behind the plate, and on the Nationals Park mound Stephen Strasburg shook his head. In the second inning, with two strikes on Grady Sizemore, Strasburg wanted to throw a fastball up and away instead of what Lobaton asked for. Lobaton nodded. In Strasburg’s disagreement, the catcher saw conviction and focus. And then he saw Strasburg blow a 94-mph fastball past Sizemore.

“Yeah, he’s here,” Lobaton thought. “Today is going to be a good day.”

From the start of the Washington Nationals4-0 victory over the Philadelphia Phillies on Sunday afternoon, Strasburg seized full command. He stared down Cole Hamels, dominated for seven scoreless innings and laid claim to his spot atop the Nationals’ rotation. The Nationals scored only once off Hamels, as Denard Span remained a wrecking ball atop their lineup. They added three more runs in the eighth. But for the majority of the afternoon Strasburg outdueled Hamels, striking out 10 and allowing only three hits.

“He was focused on every hitter,” Lobaton said. “He could see the pitch, that he really wants something, a pitch that he can execute. And he did it today. That’s what you want. I want that guy. I don’t want that guy that’s just following everything. I want that guy that’s able to say, ‘No, I don’t want that pitch. I want my pitch.’ And he did it today.”

The notion that Strasburg lagged behind the rest of the Nationals’ starters had begun to take hold before Sunday. His place in a hypothetical playoff rotation — him or Tanner Roark: who you got? — bloomed into bar room banter and talk radio fodder.

Can Strasburg be relied upon in big moments? Sunday, his team needed a victory to salvage a series split. It had a chance to capitalize on the Atlanta Braves capsizing out west. His offense wilted against one of the best left-handed starters in the game. What else you got?

“From a starting perspective, everybody is giving us a chance to win every day,” Manager Matt Williams said. “But yeah, Stephen is the guy we went to the first day of the season. He’s the guy we went to after the break. He’s proven why he’s a really good pitcher.”

In his last start, in Miami against the Marlins, Strasburg allowed one run in seven innings. He continued Sunday to build off the work he had done in the bullpen with pitching coach Steve McCatty. “I figured out some things,” Strasburg said. Without elaborating, Strasburg suggested he had tweaked both his approach and, in a minor way, his mechanics.

“Just try to get more consistent with all my pitches, locate them a little bit better,” Strasburg said. “When you can do that, it’s easier to execute the game plan.”

From center field, Span noticed a critical change. Strasburg rifled his fastball inside more than Span could remember seeing. Hitters accustomed to diving over the plate — a tactic Strasburg deplores — started to back away.

“Normally, he’s throwing his fastball middle-away, middle-away,” Span said. “Guys were able to kind of cheat to his fastball. Ask any pitching coach, any player that plays this game: When a pitcher is pitching inside effectively, it just makes it tougher.”

From the dugout, Williams saw Strasburg control his fastball better than in any prior start this season. He also pinpointed a wicked curve. Strasburg rifled a 95-mph, shoulder-high fastball past Jimmy Rollins in the first inning. The next batter, Chase Utley, took a 3-2 curveball below his hands, right on the corner, for strike three.

Strasburg emphasized his follow-through, driving fastballs through the strike zone. “He had something on the ball different today, just on the end,” Lobaton said. As he upped his NL-leading season strikeout total to 177 in 1511 / 3 innings, Strasburg struck out five Phillies with his fastball, three with his curve and two with his change-up.

“You really got to do your best to pound the strike zone with the fastball early,” Strasburg said. “Get that going early, get the feel for that, hopefully all your other pitches fall in place.”

Before the game, Lobaton discussed with Strasburg which hitters he needed to throw change-ups in the dirt against. When he needed to, Strasburg buried them — Ryan Howard whiffed at one that nearly bounced on the plate in the fourth. Lobaton could think of one mistake — an inside fastball he left over the plate that Rollins smacked for a single.

“Other than that, he was putting the ball anywhere he wanted,” Lobaton said. “He was awesome. Sometimes, the way you pitch can control the game. He was working fast. He could throw any pitch in any count. That’s him. I know he can do that.”

Once Strasburg exited, Tyler Clippard and Rafael Soriano retired six straight hitters. Building off the end of Friday night’s 2-1 loss and Jordan Zimmermann’s seven scoreless innings Saturday, Nationals pitchers closed the series with 21 consecutive scoreless innings.

Span remained a force. He drove in the Nationals’ first run against Hamels and scored the second in the eighth, racing home from first on Anthony Rendon’s double. Span reached base three times, extending his streak of games reached safely to 29, the longest in the majors this season. He also stole two bases, giving him 23 in 25 tries, just three off his career high.

“This is something I’ve been working since the day I got drafted at 18,” Span said. “I probably feel the slowest I’ve ever felt in my career, just as far as getting older. [Nationals coach] Tony [Tarasco] has been in my ear since spring training started, before every game. He’s giving me something to get me ready. It’s just been a joy to see my hard work translate onto the field.”

The Nationals own a season-high 31 / 2 game lead over the Braves in the National League East after Atlanta suffered a 10-inning loss to the Padres in San Diego. The Nationals have stabilized with two straight wins, while the Braves finished Sunday with a six-game losing streak and four wins in their past 14 games.

Once the ninth inning ended, Strasburg ambled out of the dugout to line up and shake hands with teammates. One performance may not silence those who would take Doug Fister and Jordan Zimmermann and Roark over him. Maybe it shouldn’t. But the Nationals would have no problem taking Strasburg.

“They know,” Lobaton said. “The GM did it and the manager did because they trust him that he can do that. I know he can do that. I’ve seen it in spring training. I’ve seen in the season that he’s able to do that. I know if he focuses, he’s going to get better.”