The Washington Nationals needed two hands to count the good parts of their 18-1 win over the Miami Marlins on Monday night at Nationals Park.

The Nationals scored 10 runs before the Marlins recorded six outs. They did that with an RBI triple from Trea Turner, a two-run homer from Juan Soto, a 446-foot solo homer by Josh Bell, the first homer of Tres Barrera’s career, a three-run homer from Turner, an RBI double by Josh Harrison and an RBI single from Gerardo Parra. Ross Detwiler, the Marlins’ opener and a former Nationals pitcher, faced 11 batters, yielded all four of those homers and exited. David Hess relieved Detwiler and found trouble, too.

And Jon Lester, the Nationals’ starter, even logged a single and a two-run, 419-foot homer off Hess in the fifth. But somehow, in a game stocked with offense, the best development for Washington (44-49) came with Lester on the mound. The 37-year-old lefty logged his best start of a disappointing year with the Nationals: seven innings, zero runs, six hits, no walks and a season-high seven strikeouts on 81 pitches.

“Sometimes when you struggle, you kind of look for things that aren’t there,” Lester said when asked if he was helped by extra rest over the all-star break. “To kind of get away, and just forget about mechanics, forget about throwing a baseball, working out, all that stuff, just kind of get back to neutral. That’s always good for us. So that was kind of where I was at. Kind of cleared my mind a little bit. Kind of went back to basics.”

Yes, it was one game. Yes, it was one game against the last-place Marlins. And yes, the last-place Marlins were without Starling Marte, Jazz Chisholm Jr., Brian Anderson, Garrett Cooper and Jesús Sánchez. But Lester’s season has called for measuring progress by the teaspoon. That he carved up a depleted lineup — and a team spending less on its whole roster than the Nationals are on Max Scherzer and Stephen Strasburg alone — was worth noting because of how he fell into break.

Before Monday, he had allowed 17 earned runs in 13⅓ innings across his previous four starts. His ERA was 5.54. By some metrics, he was one of the major leagues’ least-effective starters, falling well short of the expectation that, in the fourth spot of a stacked rotation, he would bring durability and consistent length.

Yet any baseball narrative can change for a few hours. Here was hard proof.

“I’m just glad that I was able to pitch some innings,” said Lester, who lasted only 2⅓ innings against the Marlins on June 25. “It’s been kind of a struggle lately with innings. For the simple fact of just being able to get deeper in the game, my pitch count was manageable at the time, so all those things are positive.”

“He was throwing strike one all night long and pounding the strike zone,” Manager Dave Martinez said. “He was making his pitches with all his pitches: change-ups, a couple of curveballs that were really good. His cutter was good. Just really attacking.”

Lester’s best friend Monday was a backdoor cutter on the outside of the plate to righties. He used one to strike out Jon Berti looking in the first, Adam Duvall swinging in the fourth and Jesús Aguilar swinging in the sixth. His 10 total whiffs, his most in a month, were also tied for his third most of the year. Only 22 balls were the fewest of his season.

It was a sharp contrast to how, in recent starts, he nibbled on the edges because his velocity is not what it once was, and his secondary pitches — a change-up and curve — have lagged since he missed most of April on the coronavirus-related injured list. Lester felt his confidence build with each zero. He worked around a leadoff single in three of his seven innings, leaning on cutters and four-seam fastballs. His 40 four-seam fastballs were good for 12 called strikes and five empty swings. He didn’t throw more than 13 pitches in an inning.

And then he took Hess deep.

“Just a blind squirrel finding a nut, I guess,” Lester said with a laugh. “Obviously, that was a pretty cool moment.”

On that swing, at a 1-0 fastball, Lester became the oldest pitcher to homer since 42-year-old Bartolo Colon did in May 2016. It was the fourth homer of Lester’s career, the others in 2017, 2018 and 2019 with the Chicago Cubs. It helped turn the game into a full-on blowout, the sort that ends with Marlins catcher Sandy León taking a turn on the mound to save the bullpen arms.

In the seventh, then, Soto rocked León’s high-and-away change-up for a three-run blast, his fifth in four games since the all-star break. That’s the most homers in any four-game stretch of his already impressive career. Still, though, Lester held the spotlight, capping an encouraging day for the Nationals’ rotation.

Strasburg spent the afternoon throwing a 32-pitch bullpen session, a nudge forward after he experienced a setback in recovery from nerve irritation in his neck. If Washington gets him back soon, and Lester builds on a flash of efficiency, the pitching staff could look a lot better than it has in the past three weeks. And that would be a major lift as they try to climb from six back of the New York Mets in the National League East.

Lester, of course, has a lot to prove in his next chance, a start against the Baltimore Orioles, then the next one, a tougher test with the Philadelphia Phillies. But no matter the opponent, and no matter what proceeded Monday, this was an important step.