Players on both Super Bowl teams say they are confused about when a hit is legal by NFL standards.
Rules designed to make the game safer are also making players uncertain about which hits are considered clean and which ones could lead to a fine.
San Francisco tight end Vernon Davis wondered if two-hand touch is in the future for the NFL.
"I think the rules will change a lot," he said Tuesday. "There's already no helmet to helmet. Might be flag football, maybe."
Baltimore Ravens safety Bernard Pollard, one of the league's hardest hitters, warned against trying to take collisions out of the game, as long as they are clean.
His 49ers counterpart, All-Pro Dashon Goldson, says defenders keep this in mind when they take the field:
"Do your best and then hope you don't get a letter (with a fine) in your locker on Wednesday," he said.