Trumpets blare when Edwin Díaz emerges from the bullpen, but these days, a sad trombone might be more fitting.

The former Mets closer is struggling mightily in his first year with the Los Angeles Dodgers — an injury-and-inconsistency-marred season that plummeted to a new low Thursday night.

Díaz surrendered three runs on four hits in the ninth inning of the Dodgers’ 5-4 loss to the Milwaukee Brewers in L.A., recording only two outs.

It was the fourth blown save in 10 opportunities for Díaz, who fell to 2-2 with an 11.57 ERA in 14 appearances.

“It’s frustrating, because I know my ability,” Díaz, 32, said afterward. “I know what I can do on the mound. To not be able to do it, it sucks.”

Finding a rhythm has not been easy for Díaz, who spent more than three months on the injured list after undergoing surgery in April to remove loose bodies from his prized right elbow.

Since returning on July 29, Díaz has allowed at least one run in five of his seven appearances and has blown three of four save chances.

Díaz blew only three save opportunities all of last year with the Mets, when he earned his third All-Star appearance and pitched to a sterling 1.63 ERA with 28 saves.

“I know I’m struggling,” said Díaz, whose lack of fastball command doomed him on Thursday night.

“I want to do the best thing for the team. At the end of the day, if they give me the ball in the ninth, I will try to do my job. If they give me the ball in another inning, I will try to do my job. I’ve just got to get better, be consistent.”

Tanner Scott, who filled in as the closer during Díaz’s injury absence, has a 2.25 ERA and 16 saves in 18 chances this year, though the Dodgers value the left-hander’s versatility in a variety of late-inning roles.

Dodgers manager Dave Roberts did not sound like someone eager to make a change at closer. Asked about that possibility after Thursday’s loss, Roberts responded, “Give me another option.”

“It’s just not that easy when a guy’s done it for seven, eight years, whatever it is, to change routines,” Roberts said. “Part of my job is to give him the best opportunity to prepare and have success, and then it goes to the player to kind of go out there and do their job.”

In December, the back-to-back defending-champion Dodgers signed Díaz to a three-year, $69 million contract with deferrals, barely edging the Mets’ offer.

Díaz’s departure surprised Mets owner Steve Cohen, who told radio broadcaster Howie Rose in a February interview, “I did find that one perplexing.”

“Not sure exactly how Edwin arrived at that decision,” Cohen said. “Obviously, it’s a personal decision on his part, and I thought we made a pretty respectable bid.”

Díaz was a fan favorite in Queens, where he spent seven years and became known for his electric fastball and similarly electric entrance to “Narco” by Blasterjaxx and Timmy Trumpet.

His was one of two bidding wars the Mets lost to the Dodgers last winter. L.A. also won the sweepstakes for four-time All-Star outfielder Kyle Tucker, whom they signed to a record-setting four-year, $240 million mega-deal.

Tucker, too, has disappointed, entering Friday with a .236 average, 11 home runs and a .712 OPS through 115 games.

Shortly before they lost Díaz, the Mets signed reliever Devin Williams to a three-year, $51 million contract. Williams is 3-2 with a 4.66 ERA and 16 saves in 19 chances. He landed on the injured list this week with a right shoulder strain.