PITTSBURGH — The good vibes of snapping the franchise’s longest losing streak in four years lasted all of about 21 hours for the Mets.

Returning to PNC Park on Sunday with a chance to win a series, the Mets maybe felt the effect of Pete Alonso’s absence from the lineup for the first time in the almost five complete games they have played without him.

The added “level of competitiveness” that manager Buck Showalter implored his players to find during a recent closed-door meeting was absent in a 2-1 loss to the Pirates. The Mets managed only three hits and have now lost eight of nine games as they await the Subway Series beginning Tuesday at Citi Field.

“As a team Buck talked to us and we have just got to continue to fight and stop worrying about what’s going to happen,” Francisco Lindor said. “We have got a sense of urgency. Just work as hard as you can. Be accountable for your job, be a professional baseball player and just get the job done.”

Alonso is expected to miss at least three weeks with the bone bruise and sprained left wrist he sustained after he was drilled with a pitch by Charlie Morton on Wednesday. The absence of MLB’s home run leader has left the lineup vulnerable to performances like Sunday’s.

“Absolutely, we miss [Alonso], but we still have got to get the job done,” Omar Narvaez said. “We don’t rely on just one hitter. We’re still a good team.”

Carlos Carrasco folded in the middle innings in his last start and Showalter wasn’t about to repeat history. The right-hander was removed after 4 ²/₃ innings in which he allowed two earned runs on six hits with three walks and one strikeout. Carrasco pitched strong through five innings in his previous start before the Braves scored three in the sixth against him. Showalter said the fact Carrasco was on normal four days’ rest instead of extra played into removing him at 81 pitches.

Jeff McNeil’s homer leading off the fourth produced the game’s first run. The extra-base hit was only McNeil’s third since May 1, when he had last homered. McNeil jumped on a full-count fastball from Mitch Keller and cleared the right-field fence. Brett Baty drew a two-out walk in the inning and Mark Canha was hit by a pitch, but Keller retired Narvaez to escape.

Carrasco surrendered a homer to Jack Suwinski leading off the bottom of the inning that tied it 1-1. Suwinski swatted a hanging breaking ball high off the right-field foul pole before the Pirates added another run in the inning on Tucupita Marcano’s RBI single that followed Ji Hwan Bae’s double.

Showalter removed Carrasco with Suwinski coming to the plate with two runners on and two outs in the fifth. Lefty Josh Walker entered and struck out Suwinski.

“I think I went too short today,” Carrasco said. “I just tried to keep the game there at 2-1, and in the last inning I just lost control a little bit. I couldn’t find my changeup. But I am glad I could keep us close and I felt pretty good today.”

Keller crushed the Mets by allowing one run on two hits with seven strikeouts and one walk over seven innings. The Mets managed only one hit after the fourth inning and their woes included a pitch-clock violation on pinch-hitter Luis Guillorme leading off the eighth inning for Strike 3. Guillorme was late getting set in the batter’s box.

“That one surprised me, because Louie is such a sharp guy with that type of stuff,” Showalter said. “It’s something we have got to do better. … It was a very important at-bat and it just got away from him.”

Lindor would like nothing better than for the Subway Series to spark the team’s turnaround.

“That’s a playoff atmosphere without being in the playoffs,” Lindor said. “It’s always a great show when two fan bases in the same city go at each other.”