PHOENIX (AP) -- The NFL concentrated on player safety on the second day of the owners meetings, yet didn't vote on the most contentious rule proposal.
Concerned with how it will be officiated, owners delayed voting Tuesday on a rule change that would ban offensive players from using the crown of their helmets against defenders in the open field.
After approving two other rule changes to enhance player safety, they stalled on the more contentious issue. NFL senior vice president of football operations Ray Anderson said the owners plan to vote on it Wednesday before the meetings end.
The potential change that has drawn the most attention — yes, even more than eliminating the infamous tuck rule, which seems to be a foregone conclusion — is prohibiting ball carriers outside the tackle box from lowering their helmets and making contact with defenders with the crown.
New York Giants owner John Mara, a member of the competition committee that has recommended the change, said there was even "a chance" a vote could be tabled until the May meetings in Boston.
"There was a spirited discussion," Mara said, adding there was concern of how the rule would be officiated.
Broncos coach John Fox believes passing the rule will not make for a huge challenge for players.
"Right now, the simple equation is they want the helmet used for protection, not as a weapon. I think that message gets across," Fox said. "It's slowly gotten across as far as the passing game. Now there are rules on the table that are going to involve the running game as well.
"They will adapt. They have in the past and (they will) moving forward."
The owners outlawed peel-back blocks anywhere on the field; previously, they were illegal only inside the tackle box. A player makes a peel-back block when he is moving toward his goal line, approaches an opponent from behind or the side, and makes contact below the waist.
The penalty will be 15 yards.
"... really under no circumstances will you be permitted to block low below the waist when you're blocking back toward your own end line," said Rams coach Jeff Fisher, co-chairman of the competition committee.
Also banned is overloading a formation while attempting to block a field goal or extra point. Defensive teams can now have only six or less players on each side of the snapper at the line of scrimmage. Players not on the line can't push teammates on the line into blockers, either.
The alignment violation is a 5-yard penalty. The pushing penalty is 15 yards for unnecessary roughness.
"There were injuries, yes," Fisher said. "Talking to coaches and the players, it's just not something they look forward to doing. It's like, 'Oh, we scored again? We have to go out there and protect, kick an extra point or try?'"
Protecting tacklers against helmet hits has become more dicey.
The competition committee's examination of one week of play last season found five instances where a ball carrier was not protecting the ball or himself and lowered his helmet to make contact with a defender. Dean Blandino, recently promoted to vice president of officiating, noted that five in 16 games was significant enough to consider banning the act.
"In all fairness, it's going to be tough on the officials, it's going to be tough to make that determination at live speed with one look," said coach John Harbaugh of the Super Bowl champion Baltimore Ravens.
"We want to make a serious attempt to get the shoulder back into the game. We are not saying the ball carrier cannot get small. We are not saying the ball carrier cannot protect the football, because if he is going to go down to cover the football, if the shoulder goes down, we know the head goes down, we understand that.
"Protecting the football is OK, providing you do not strike with the crown of your helmet, and that is what we are trying to differentiate."
Blandino said the league wants flags thrown only on the obvious calls. He also said in cases where a player is not penalized, he could still be subject to a fine if video review after the game determines he made contact with the crown.
The penalty will be a spot foul for 15 yards.
New senior director of officiating Alberto Riveron said if the offensive and defensive player are both committing the foul, it would be an offsetting penalty and the down replayed.
Riveron said the key to officiating the play is in showing the officials more plays that are legal.
"That will be a great way to train because as we know it, most of the shots we have seen are legal, most of the contact is legal," he said. "We are trying to get that one individual situation where the head is lowered — and you can see on the field, you can see a player put his head down — and the contact is with the crown and you can see it."