Beckham and fellow receivers Victor Cruz and Sterling Shepard made headlines last week after vacationing in Miami on their day off to celebrate their regular-season-ending victory over the Washington Redskins.
Beckham then struggled in Sunday's loss to the Green Bay Packers in the wild-card round, finishing with four catches for 28 yards and dropping multiple key passes from Manning, including a potential touchdown in the first quarter.
"You've got to learn that the perception of things makes it different," Manning said Monday, less than 24 hours after the Giants' season-ending 38-13 loss in Green Bay. "You do things, you've got to back it up.
"I don't think it had an impact on the game. I thought we had a great week of practice. Guys were making plays and running around and intense and focused and everything [was] good. Unfortunately we just didn't have it yesterday."
Beckham did not speak to reporters Monday. He was calm and composed during his postgame media conference Sunday, saying, "these are the learning experiences, as tough as they are."
But after speaking to the media, Beckham allegedly punched a hole in a wall outside the locker room, according to ESPN's Sal Paolantonio, who also saw Beckham banging his head against a door.
Both general manager Jerry Reese and coach Ben McAdoo spoke with Beckham on Monday morning. Reese said he would "definitely, 1,000 percent hold him responsible" for the hole in the wall if Beckham was responsible. McAdoo made it clear he wasn't happy with the behavior.
"We take full responsibility, I take full responsibility," McAdoo said. "That is no way to carry yourself after a ballgame. Let's move on."
It's going to be a long offseason for Beckham after he struggled in his first career playoff game. His season was filled with ups and downs, including at least six known fines, and his off-the-field behavior has come under fire.
"I see a guy who needs to think about some of the things that he does," Reese said. "Everybody knows that he's a gifted player, but there have been some things that he's done that he needs to look himself in the mirror and be honest with himself about some of the things that he's done.
"I think he'll do that. We'll help him with that, but he has to help himself, and we believe he'll do that. He's a smart guy but sometimes he doesn't do smart things."
Beckham, Cruz, Shepard and receiver Roger Lewis took a private jet to Miami on Jan. 1 after New York's 19-10 victory in Washington. They were captured on social media partying with a group of celebrities, including Justin Bieber, at a nightclub and were photographed on a yacht the following day.
Beckham, 24, has made the Pro Bowl in each of his first three seasons. He mentioned several weeks back that it was important for him to keep his composure on the field and sideline because some of his younger teammates are watching.
"We all have had to grow up in different times in our lives," Reese said. "I think it's time for him to do that. He's been here for three years now. He's a little bit of a lightning rod because of what he does on the football field, but the things he does off the football field, he has to be responsible for those things. We'll talk through it and I believe -- I know -- he's a smart guy. I believe he understands he has a responsibility being one of the faces of this franchise. I think he'll accept that responsibility."
ESPN's Jordan Raanan and The Associated Press contributed to this report.