BALTIMORE — It’s going to be a long final two months of the 2023 season for the Mets.

They extended their losing streak to four games on Friday night with a 10-3 loss to the Orioles. The streak began on Tuesday, the day of the trade deadline, which signified the end of the season.

For good measure Friday, two of the biggest hits for the Orioles came from former Mets free-agent bust James McCann, who had a two-run single against John Curtiss in the fourth inning and a two-run double in the sixth against Phil Bickford.

McCann finished the night with five RBIs after he entered the game with just 10 this season.

The Mets’ makeshift bullpen — and pitching staff as a whole — will certainly be exposed the rest of the way and Friday was a look at what’s likely to come.

Manager Buck Showalter said he believes the team is feeling the effects of having traded many of their stars away — and playing poorly as a result.

“Guys are human beings, but we have been outplayed, I know that,” Showalter said of the team’s response to the fire sale. “We have to play better and some people getting an opportunity have to take advantage of it. … We’re just not pitching very well and not scoring many runs. It’s a bad combination.”

Coming off a series sweep at the lowly Royals, the Mets visited a resurgent Orioles team that’s in first place in the tough AL East.

With Max Scherzer and Justin Verlander gone, David Peterson made his first start since June 27 following a demotion to the bullpen. On a pitch count, Peterson pitched around three walks without giving up a run, but he lasted just three innings on 52 pitches.

Peterson will have plenty more starts down the stretch and he’s already eyeing the future.

“It’s an opportunity for the team and for myself,’’ the lefty said. “We’ve got plenty of games left. We have to play as hard as we can and give everything we’ve got and see where we’re at.”

The results, so far, have not been encouraging.

“Things have obviously changed with the mindset of the organization from where we started the year, but that doesn’t mean we don’t play the rest of the games,’’ Peterson said. “We’ve got to finish strong and show the front office what we have going into the offseason.”

Judging by Friday night, they’ll need some new relievers, as the six who followed Peterson were mostly terrible. And a lineup that was shutout on Wednesday and scored just a pair of runs on Thursday at Kansas City, was quiet again Friday.

Francisco Lindor doubled with two outs in the first, but was caught trying to steal third to end the inning.

The Mets loaded the bases with one out in the sixth, as Dean Kremer walked three in a row before Lindor dunked a two-run single to right to tie the score at 2-2. Kremer exited for Mike Baumann, who got Pete Alonso to hit into an inning-ending double play.

A Ryan O’Hearn single scored Jordan Westburg for the go-ahead run in the sixth inning before McCann blasted a shot off the high wall in left that would have been a homer in every ballpark other than Camden Yards.

That was part of a four-run sixth inning that Baltimore matched with a four-run seventh, as Bickford and Reed Garrett combined to give up eight runs in one inning of work spanning those two frames.

The Mets didn’t recover and they fell to 50-59. They can match a season-high by falling 10 games under .500 with another loss on Saturday.

If that doesn’t happen Saturday, it seems certain to occur at some point this year, as the current roster needs nearly everything to go right just to win a game.