Sandy Alderson offered a blunt appraisal of his team’s offense, a unit that has looked lost in clutch situations and has stopped hitting the home runs that once sustained it.

But on Thursday, the general manager indicated that the Mets might not swing the kind of trade that brought in slugger Yoenis Cespedes last summer.

Instead, Alderson said improvement from the players they already have — not the major splash that many regard as a quick fix — will be the likeliest path toward getting the Mets back on track.

“There’s no single acquisition, at least that I can see, that’s going to change what’s transpired over the last two months,” Alderson said. “It’s going to have to come from within.”

The Mets began a four-game series with the Cubs ranked 13th of 15 teams in the National League at 3.58 runs per game and last with a .233 average. They also were below the league average in on-base percentage (.305) and slugging (.399).

The home run had been their savior, but they had slipped to fourth in the National League with 97 homers. “The power has more or less disappeared,” Alderson said.

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Indeed, the Mets have struggled to hit overall, though their weakness with runners in scoring position has been particularly debilitating. They began the day hitting an NL-worst .205 in that situation, 27 points lower than the Phillies, who rank second to last.

The Mets have come to no easy conclusions about their struggles.

“Whether we’re chasing poor pitches in the strike zone as opposed to being a little more selective is maybe a different story,” Alderson said. “But it’s hard to tell exactly what has happened.”

Injuries have played a part. Lucas Duda is two weeks away from baseball activity because of a stress fracture in his back. David Wright has had neck surgery that could sideline him the rest of the season.

Catcher Travis d’Arnaud only recently returned from an extended absence with a shoulder injury. But he has yet to find his stride at the plate and was hitting only .203 entering Thursday night.

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Underperformance also is part of the equation. The clearest case has been Michael Conforto, whose average slipped to .222 before his demotion to the minors. The Mets hope he forces a promotion quickly.

Otherwise, it doesn’t appear that the Mets are in the mode to make a splash. Alderson said he doesn’t intend to trade any “blue-chippers,” and earlier this week, a team source told Newsday that top prospect Amed Rosario is virtually untouchable in trade talks.

Although the Mets held a private workout for Cuban star Yuliesky Gourriel, competition for his services could be stiff, and it’s unclear what he could contribute immediately.

“It’s frustrating for everybody that we’re sort of back at square one on the offense,” Alderson said. “But again, we’ve got the personnel to be better and I expect we will be.”