Eli Manning knows it can happen. It almost happened to him and, he fears, it could happen to Odell Beckham Jr. as long as the star wide receiver continues to live life with the Giants without a contract extension.

The uncertainty can weigh on a player.

“Unfortunately, it can,’’ Manning said Monday afternoon at the Guiding Eyes for the Blind Golf Classic at Mount Kisco Country Club.

Manning knows of what he speaks. Back in 2015, he was in contract negotiations, going through all the spring work and even the summer training camp without a deal. He eventually signed a four-year, $84 million extension in the second week of September, two days before the regular-season opener.

Looking back, Manning recalls that waiting game was no fun.

“Even though it wasn’t really something that was on my mind you just had to keep answering questions about it,’’ Manning said. “It’s not something I discussed with people, but for whatever reason it becomes an issue. I didn’t harp on it, I didn’t worry about it, but the fact that it was in the papers or you had to answer about it, it can become a hassle.

“Hopefully, obviously everything with Odell and that, whether it gets solved or whatever, it’s something that you don’t have to keep answering about it.’’

Manning and the Giants have a busy week, as Tuesday is the start of a mandatory three-day minicamp and Beckham will be in attendance. He has no desire to lose money here — in accordance with the collective bargaining agreement, a player can be fined $84,435 for missing the three-day camp — as he continues his goodwill approach by giving the Giants what they want.

In the organized team activity practices he attended this spring, Beckham was limited, coming off surgery to repair a fractured left ankle. He was far more of an onlooker than he was a participant. He stretched with the team and went through a few jog-through pace individual drills, then went off to the side to work with trainers as the rest of the team stayed on the field for 11-on-11 and 7-on-7 work.

“Very little on-the-field work,’’ is Manning’s description of what Beckham did during the OTAs. “Just kind of getting in the meeting rooms and he’s been there for some of the walk-throughs and stuff. It’s important to just kind of hear the plays, hear the formations, hear everything so he’ll have a good idea of what’s coming up.’’

It would not be a surprise if Beckham remains limited at the start of training camp in late July. The Giants are of no mind to accelerate Beckham before he is completely ready to go and, once he is given the green light in camp this summer, expect he will be eased in slowly.

There might be a slight uptick in what Beckham is allowed to do this week, but it will be baby steps, not leaps ahead.

“I think he’s supposed to be allowed to do a few things this week, whether it’s just routes versus air, or certain things that we can start working on,’’ Manning said. “A lot of the routes are very similar, there are a few that are a little different, and we can start working on those and start getting the timing down.’’

Last year, Beckham was healthy but did not attend any of the 10 OTAs, opting to work out in Los Angeles. That he showed up periodically this year is a strong indication he is taking seriously the Giants’ plea for him to upgrade his entire professional portfolio before they reward him with a long-term contract extension. His attendance was a good-faith gesture by Beckham, and the Giants view it that way. There is plenty of time prior to the start of the regular season for the two sides to come together on a new deal that would make Beckham the highest-paid wide receiver (in excess of $17 million per year) in the NFL.

While Beckham watched, Manning threw to Sterling Shepard, tight end Evan Engram and got to see what rookie running back Saquon Barkley (“I’ve been impressed with his maturity,’’ Manning said) can add to the offense.

“There are still a lot of weapons,’’ Manning said, “and then you throw Odell in there and it should be better.’’