PHILADELPHIA — Here was a sight that would’ve been foreign for the Nationals the last few seasons: PJ Poulin jogging in from the bullpen to open Tuesday’s game against the Phillies.

The strategic move paid off in the bottom of the first. He pitched a scoreless frame and tamed the Phillies lefties at the top of their order. But Zack Littell, who followed him, allowed three runs over five innings in the Nationals’ 3-2 loss to the Phillies at Citizens Bank Park.

“I thought it went exactly how we had hoped,” manager Blake Butera said. “Couldn’t have been better.”

Littell, who was second in the majors in home runs allowed last season, surrendered a pair of solo shots to Kyle Schwarber and Adolis García in the third and fourth innings, respectively.

Washington’s hitters looked helpless facing Phillies starter Andrew Painter, a heralded prospect making his major league debut. Painter faced 21 batters and allowed four hits over 5 1/3 innings while striking out eight.

Butera and the Nationals hitters credited Painter for locating effectively on the edges and keeping them guessing.

The only hitter with much success against Painter was Daylen Lile, who had two of the Nationals’ four hits off Painter. Lile grew up facing Painter in travel ball and said he’s the same pitcher he was then.

Once Painter exited, Lile roped a single in the sixth. CJ Abrams advanced from first to third, then scored on a throwing error from García. The seventh inning brought drama: James Wood hit an RBI double that bounced off the foot of reliever Tanner Banks and shot into shallow right field. But Washington (3-2) couldn’t complete the comeback. Wood lined out to left field to end the game; the Nationals finished 0-for-9 with runners in scoring position and left eight runners on base.

“Felt like I had some good takes,” Wood said. “Eventually, I had to get a good pitch to hit and just hit it right at him. (Brandon) Marsh made a good play out there.”

The Nationals signed Littell to a one-year, $7 million deal this offseason with incentives to take the deal to $9.5 million and a 2027 mutual option. But Littell agreed to the deal on March 10, meaning he had less time to build up for the season.

He traveled to Washington after spring training for two exhibition games against the Orioles, then returned to the team’s training facility in West Palm Beach to make another start in a spring training game before joining the team in Chicago.

Littell said he’s still trying to get himself to a position where he can just pitch and not worry about his pitch shapes and body movements — something he would’ve focused on during a normal spring.

So the Nationals opted to use Poulin. The Nationals hadn’t used an opener since July 2019, when lefty Matt Grace was used against the Los Angeles Dodgers. Washington discussed the strategy in the years that followed but never implemented it.

On Tuesday, there was ample reason to: Schwarber and Bryce Harper mash right-handed pitching. Using an opener would create one fewer matchup for those two against Littell.

Poulin found out on Monday night that he’d be the team’s opener. He had experience as an opener in the minor leagues last season and started the Nationals’ exhibition game against the Orioles on March 23. His routine doesn’t change. It just starts earlier.

“That’s part of being a reliever, right?” Poulin said. “It’s being adaptable, being able to be known into a bunch of different situations and do your job.”

The decision to use Poulin paid dividends: Poulin struck out Schwarber in his first at-bat and got Harper to ground out.

A persistent weakness of the Nationals’ roster over the last few seasons has been the team’s lack of reliable left-handed reliever options. If they used one early, they might not have a better one later in a given game.

This iteration of the Nationals has three left-handed relievers: Poulin, Ken Waldichuk and Cionel Pérez. Poulin fits the profile of a left-handed opener, with a slider from a unique arm slot. Waldichuk pitched a scoreless seventh and eighth. Perez will likely be a high-leverage reliever against lefties this year. All three have contributed to a bullpen that has performed well through five games.

But the bullpen couldn’t help the Nationals beat the Phillies. Littell was solid in his first outing with the Nationals. He threw 53 of 75 pitches for strikes, got ahead of hitters and had short at-bats.

Littell faced Harper in the fifth with the bases loaded. Harper hit a grounder to first baseman Luis García Jr., who made the team’s lone error. That proved to be the difference.

Littell, though, was his own harshest critic after the game. He felt he could’ve executed better. And perhaps that would’ve put his team in a better position to win.

“I’m not going to sit here and make excuses,” Littell said. “It is what it is: You got to find a way to come out here and get outs. Tonight, I just didn’t make quite enough pitches.”