If Giants ownership is already convinced coach Ben McAdoo is going to be dismissed after the season, there might be no reason to wait until Jan. 1, especially considering three of the last four games are at MetLife Stadium, and these final home games could spark some of the ugliest moments in franchise history. An ESPN report stated McAdoo “could be’’ fired as soon as Monday. Fans are irate at the way McAdoo ended Eli Manning’s 210-game starting streak, even though co-owner John Mara was completely on board with getting a look at Geno Smith — the starter Sunday for a 24-17 loss to the Raiders — and rookie Davis Webb at quarterback. How irate? Protests are scheduled for next Sunday’s game against the Cowboys. A group of ex-Giants are also talking about standing on the sideline for next week’s game wearing Manning jerseys, FOX Sports reported. McAdoo, asked if he is concerned with the reaction of Giants fans for the next home game, said, “No, I am not concerned. Listen, I understand where the fans are coming from. It I was on the outside looking in, I’d feel the same way they feel. You know Eli and I have a tremendous relationship. I think the world of him and it was hard for me emotionally. The beginning of the week, once you make a decision, you have to stick with it and I appreciate the way Eli handled things this week.’’ Seeing Manning’s former teammates sticking up for him would at least be a heartening sight for Giants fans — or the ones who show up, at least. Former players on the field may be sending a message to Giants ownership; loads of empty seats would be the fans’ contribution to the effort. “Basically what we’re trying to do is a peaceful protest, a little solidarity for Eli,’’ Matt Meyer, a longtime Giants fan, told The Post. “We’re trying to encourage our friends on Giants Facebook groups and message boards to not go in, not resell our tickets. Let everyone see this.’’ The plan is to tailgate, as usual, at MetLife Stadium, and remain in the parking lots during the game to show the fans’ displeasure in the form of empty seats. Money is also being raised to fly a plane with a message over the stadium, similar to what transpired in 1978, when a banner reading “15 Years Of Lousy Football — We’ve Had Enough!’’ flew over the stadium and helped usher in a regime change.