If Matt Harvey’s pitching hasn’t been underwhelming enough, his off-field ventures are again becoming a potential problem for the Mets.

A day after Page Six reported Harvey traveled to Los Angeles for a night of partying following the team’s arrival in San Diego last week, general manager Sandy Alderson acknowledged the pitcher’s nocturnal habits can be a problem.

And the reaction in the clubhouse to Harvey was equally unsympathetic.

“It’s just, what are you doing?” one Mets player said.

Harvey pitched one inning in relief the night after his sighting in Los Angeles and allowed one run on a homer in the team’s victory over the Padres.

“I think it can be a problem if it affects a player’s or a pitcher’s preparation for work the following day or the next several days and I am not sure that was the case here,” Alderson said Tuesday. “[But] I think the other thing I have tried to keep in mind is pitching out of the bullpen is different than pitching out of the rotation and part of the preparation for that role is recognizing you can pitch any day at any time and as a result you have to be a little more conscientious about what else is going on in your life in order to be prepared on a moment’s notice to pitch.

“That is part of the realization that maybe’s he’s had over the last few days. So to answer the question as succinctly as I can, ‘Yeah, it can be a problem.’ I don’t think it was in this case.”

Alderson was asked if he was upset by the Page Six report.

“Usually I get upset if a report is unexpected, so I guess the short answer is no,” Alderson said.

And the GM noted that Harvey, at this point in his controversial career, is always in the public’s eye.

“It’s like a borderline pitch [for a batter],” Alderson said. “In his case it always gets called a strike. He probably learned something from it.”

Last season Harvey was suspended by the team, forcing him to miss a start, after he failed to show up for a game at Citi Field. Harvey, who had attempted to call in sick, later acknowledged he had stayed out late the night before.

Harvey was also absent from a workout at Citi Field before the 2015 NLDS, indicating he had gotten caught in traffic.

Manager Mickey Callaway said he met with Harvey on Tuesday and told the pitcher to avoid becoming a distraction.

“It is bad in the sense that it’s getting publicity,” Callaway said. “Matt has to be aware of that. The things he does, right or wrong, are going to be brought to the forefront and we have to make sure it’s never a distraction for him or the team.”

Harvey, who is 0-2 with a 5.76 ERA, has appeared in three games in relief since his reassignment from the rotation. Team officials are still hopeful for a turnaround that would allow him to possibly rejoin the starting rotation. Callaway was asked if the bullpen move was designed at getting Harvey right or helping the team.

“It’s really just to help our team in general,” Callaway said. “Whether it’s all of a sudden he becomes this big weapon in the bullpen or he has to go back into the rotation to give us some meaningful starts this year, so I think there is not one main goal. We have to work diligently every day to make him a better version of what he’s been and kinda go from there and see what happens.”

Alderson would like to see Harvey view the bullpen role as more an opportunity than a demotion.

“I think he understands at this point that while the bullpen, he might view it as a relegation in some way, that his only way back to the rotation is through the bullpen and being successful in a meaningful role in the pen,” Alderson said.