NEW YORK -- For Edwin Díaz, Friday night was uplifting. Striking out Ronald Acuna Jr. and Ozzie Albies in succession to preserve a tie game at Citi Field, Diaz enjoyed one of the more positive moments of what has otherwise been a nightmare first season in Flushing.

Saturday night, by contrast, was a study in frustration. Diaz departed the Mets’ 9-5 loss to the Braves due to right trapezius muscle tightness. While Diaz does not consider the issue serious, it nonetheless added another obstacle to a season full of them.

“I don’t really understand why it happened,” Diaz said through an interpreter. “When I felt like I was starting to get it going, something like this happens.”

Initially experiencing neck discomfort while warming in the bullpen on Saturday night, Diaz assumed it would dissipate as he continued to loosen. Instead, the discomfort remained as Diaz allowed a leadoff homer to Freddie Freeman, then a one-out walk to Charlie Culberson. At that point, Mets head trainer Brian Chicklo and manager Mickey Callaway visited Diaz on the mound, chatting with him briefly before removing him from the game.

“He wanted to keep pitching a little bit, but once he said that, it made no sense with the game score and everything,” Callaway said. “We’ll evaluate him in the morning and see where we’re at with him.”

According to Diaz, that plan should not require an MRI due to the perceived mildness of the issue. While Callaway insisted that “it’s really hard to say” if his closer might require a stint on the injured list, Diaz said with confidence he doesn’t anticipate an absence of that length. For as long as Diaz is sidelined, Seth Lugo figures to serve as the Mets’ primary closer.

“I don’t think it’s anything too serious,” Diaz said. “We’ll take it day by day, but I don’t think it’s going to be anything too serious.”

Regardless, the neck discomfort is the latest malady to befall Diaz since his offseason trade to the Mets from Seattle. After Freeman homered and Culberson scored to put an inherited run on his line, Diaz saw his ERA bloat to 5.55 in 54 appearances. His season includes six losses and five blown saves and, recently, a demotion to part-time closing duty.

Before Saturday, Diaz had strung together four consecutive scoreless outings, citing a sharper slider as reason for hope. But his injury casts more uncertainty over his short-term future.

“Regardless of whatever pain I have, I have to go out there and do my job,” Diaz said. “I didn’t feel 100 percent at that time, but I have to try to go out there and execute my pitches.”