Sean Doolittle coughed up a ninth-inning lead Thursday night, but his teammates picked him up. (Patrick Mcdermott/USA Today Sports)

Sean Doolittle punched and berated his baseball glove as he marched off the mound Thursday night, knowing full well his first blown save in 22 chances as a Washington National was not the glove’s fault.

The responsibility was his, and Doolittle explained his mistakes afterward. He did not fully commit to the first-pitch fastball Andrew McCutchen hit for a single, nor the first-pitch fastball Josh Bell hit out to tie the game in the top of the ninth.

“[Those pitches] didn’t have that killer instinct behind them,” Doolittle said. “Sometimes when things have been going good — and they’ve been going good for a while — I don’t want to say you let your guard down . . . ”

One blown save hardly matters to the Nationals now. Their fate has been sealed for some time. Their bullpen is as sturdy as it has ever been. Besides, the Nationals went on to win, 5-4, when Alejandro De Aza drove home Anthony Rendon in the bottom of the ninth.

But those two pitches could lead to one of two conclusions. One, as Manager Dusty Baker put it, is “better now than later.” Doolittle was never going to be perfect, so he might as well lapse in a meaningless September game.

The other conclusion is more sinister, the kind no one would dare speak, and it is this: Suddenly, doubt exists where there was little. Doolittle’s outing illuminates one of the primary questions hovering around the Nationals as they march unconvincingly through the final days of a sleepy regular season. Does what happens now, when there is no pressure, foretell anything that will happen a week from now, when pressure mounts?

If it does, then the Nationals can put their faith in Rendon and Daniel Murphy, who reached base four times each and whose back-to-back singles in the bottom of the ninth set up the go-ahead run, driven in by playoff hopeful De Aza, who also keyed the Nationals’ go-ahead rally in the seventh. If these moments say anything about October, then perhaps De Aza should earn consideration for a spot on the playoff roster.

“You’re constantly changing your mind and kind of asking yourself questions and everyone’s questions of what’s going to be our best roster,” Baker said. “He had a great game tonight.”

But if these games matter, then perhaps the Nationals should have serious concerns about their offense. The most prolific lineup in baseball for the first half of the season has the sixth-lowest on-base-plus-slugging percentage in the majors over the past month.

The team’s hitting has been stagnant for quite some time, in large part because Baker has rested regulars regularly for a few weeks. Bryce Harper, Trea Turner, Ryan Zimmerman, Jayson Werth and Matt Wieters sat Thursday. The line between needed relaxation and over-sedation is thin, and the Nationals have exhibited sluggish tendencies lately.

With the Nationals up by a run in the second, for example, Edwin Jackson could not bunt Jose Lobaton to second, so when Wilmer Difo singled a batter later, no runs scored. A half-inning after that, Jackson walked Pirates No. 8 hitter Max Moroff to start what became a two-run rally but needn’t have been much of a rally at all.

Whatever its origins, that rally provided arguments for Baker’s caution with his stars. First, Pirates starter Ivan Nova left the game mid at-bat after bunting a ball off his finger, ending his evening after two innings of one-run ball. Second, left fielder Howie Kendrick dived for a sinking line drive that bounced in and out of his glove. A half-inning later, he was out of the game, a precautionary measure because his hamstring was tight.

Most of the past two weeks have been geared toward avoiding trouble like that before October, but these weeks do matter. Jackson, for example, saw his latest big league renaissance slide softly into hibernation after six strong innings in his final start of 2017.

He might not earn a spot on the playoff roster, but after four starts in which he allowed at least four earned runs each, Jackson somehow rebounded just a few days after the loss of his grandmother. Jackson’s regular season will end with 13 starts, a 5.21 ERA and his best outing of the month.

“They say you’re as good as your last start,” Jackson said. “Then you know you want to finish it on a positive note regardless what happens after this.”

De Aza is certainly finishing on a positive note, though he is probably on the bubble for a spot on the playoff roster. His seventh-inning triple broke the deadlock before his ninth-inning single ended things, the kind of big hits that could be useful in October. The Nationals must decide if late-inning September at-bats can be extrapolated like that and hope that late-September lapses cannot be.

“Maybe in a way [it’s good] to remind myself that from the first pitch coming in, you have to be ready to go. You have to have that killer instinct,” Doolittle said. “. . . It’s a harsh reminder, and it’s a tough pill to swallow. But there are some things I can take out of this and learn from moving forward.”

The rest of the Nationals probably will not get a similar gut-punch to restore that necessary edge before October. They must hope they have a switch they can flip when they need it, one that blasts away their sleepy September ways and sends them into October wide awake.