For a moment, it appeared like the Mets' weekend struggles had snowballed into one unusual play on Sunday at PNC Park.

They were already down by three runs with one out in the first inning, the bases loaded and All-Star righty Taijuan Walker on the mound.

Walker managed to get Kevin Newman to ground a ball slowly down the third-base line, but that’s when the trouble began. He charged in on Newman’s grounder and flicked it with his glove toward the Pirates’ dugout, thinking it was foul. To Walker’s surprise, the ball was ruled fair by home-plate umpire Jeremy Riggs.

After the ball was ruled fair, the Mets were slow to react as both Walker and Tomás Nido stood in front of home plate and J.D. Davis stood halfway between third base and home. John Nogowski scored on Newman’s RBI single, while Gregory Polanco and Michael Perez were also waved around on Walker’s error, leading to a 6-0 first-inning lead for Pittsburgh.

“I was just trying to get it out because, I mean, obviously it was so close,” Walker said after the Mets rallied for a 7-6 win over the Pirates. “I just flipped it out and I thought I flipped it out into the dugout. I didn't even realize it was still in play. ... Crazy play, and obviously I was frustrated about it and I was just frustrated with myself. I wasn't getting the job done, but just one of those plays.”

Newman said he, too, wasn’t sure about the call on the field and was not sure what was transpiring, as he ended up on second base on a grounder that traveled a projected 1 foot, according to Statcast.

“I just started running, and then as I’m running to first, I turned my head and saw [Walker] swat the ball in foul territory, and everybody’s going crazy,” Newman said. “And then I heard, ‘Run to second base!’ I didn’t really know what was going to be the outcome. I didn’t know if that was a play they could review and overturn. I didn’t know if they got it right or wrong. I had a terrible view going down the line. I was kind of just standing there like, ‘What’s gonna happen?’ I had no idea.”

The infield single led Mets manager Luis Rojas to come out of the dugout to argue the call with Riggs. Rojas was ejected in the process.

Rojas said he asked for an explanation of the play, but did not receive one.

“It's not a play you see every day,” Rojas said. “And it's not replayable. ... I think we certainly deserve a chance to where the umpires can meet and talk about it. ... That's what I tried to get and I was denied.”

Despite the unusual play, the Mets managed to turn around their fortune in Pittsburgh.

Rookie Travis Blankenhorn provided a spark off the bench for the Mets as he delivered his first career homer, a three-run shot in the fourth, Dominic Smith added two RBIs and Michael Conforto delivered the big blow with a go-ahead two-run homer off Richard Rodríguez in the ninth.