The much-discussed crown-of-the-helmet rule proposal won’t be voted upon by NFL owners Tuesday in Phoenix, as expected.

NFL Network’s Ian Rapoport reported the delay via Twitter.

There will be no vote on the crown of the helmet rule proposal today. Told conversation was “lively.” Coaches spoke up. Maybe vote tomorrow

? Ian Rapoport (@RapSheet) March 19, 2013

The proposed rule would penalize a player who initiated contact with the crown of his helmet anywhere outside of the tackle box. It has drawn criticism from running backs past and present, including Hall of Famers Emmitt Smith and Marshall Faulk as well as current Chicago Bears star Matt Forte.

While it’s possible that a vote on the rule could happen Wednesday, New York Giants owner John Mara told The Associated Press that the issue could be postponed until the owners meet in Boston in May. Meanwhile, many of the league’s coaches are concerned that the new rule will be difficult to officiate.

“In all fairness, it’s going to be tough on the officials,” Baltimore Ravens coach John Harbaugh said. “It’s going to be tough to make that determination at live speed with one look.”

The league offered video clips of what would be considered legal and illegal if the rule were to pass — notably a play involving Cleveland Browns running back Trent Richardson going head first into Philadelphia Eagles safety Kurt Coleman.

– Marcas Grant, contributing editor