A supporting actor in the upcoming “Madden” film quit on Friday — just two weeks into production — allegedly over the use of the N-word and full frontal nudity … but sources close to Amazon Studios tell us the allegations are being twisted.

Here’s the deal … TMZ spoke with five members of the cast and crew for the upcoming film starring Nicolas Cage as the NFL legend, and Christian Bale as Raiders owner Al Davis … and they independently leveled some serious claims about the film’s director, David O. Russell.

Crew and cast members told us that on Friday, Russell was working with the unnamed actor on an impromptu monologue when the director allegedly said the N-word … and that upset the actor, along with others, who allegedly walked off set before they broke for lunch, and subsequently wrapped for the day.

Studio sources tell TMZ … It was actually the actor’s idea to include the N-word in the scene after a private creative conversation with the director … but ultimately the word was not used when they shot the scene. The sources stand firm — David did not say the word while shooting the scene — but declined to speculate what upset the actor and others in the moment.

We’re also told by the cast and crew sources that a day earlier, the same actor made it clear he did not want to be nude in a scene — a locker room setting — which allegedly pissed off David, and his reaction was “unprofessional.”

However, the studio sources say an intimacy coordinator tried to make the actor more comfortable and suggested different blocking, but the actor still had an issue, which is when David, calmly, said he didn’t have to be in the shot. The studio stressed that nudity was not sprung on anyone — everyone knew well in advance parts would be on display.

Studio sources also noted that the door for the actor to return to production is not closed … and “conversations” are ongoing.

One “Madden” individual told us production had been a “mess” with conflicts, like the aforementioned allegations … and tensions were being exacerbated by Nic and Christian, who are both true Method actors — portraying their characters with an intensity that doesn’t end when the cameras stop rolling.