Coffee & Pizza

I think I noticed that throughout the entire movie Denzel and Crowe are never in the same shot together. They keep facing off but from a distance and the camera just switches each of between - most evident in SID's train escape scene and when SID breaks Parker out of the prison van. Only in the first scene in the VR world and the ending rooftop fight are they physically fighting. But in the rooftop fight, I'm pretty sure in all those shots one or both of them are stuntmen. And in the opening VR fight, they only show Denzel with the back of Crowe's head and have Denzel's face blocked by a pillar when they show Crowe's face, so I'm not convinced those aren't stuntmen/stand-ins too. Were the two of them never actually on set at the same time? Is that possible?