BOCA RATON, Fla. -- The NHL Players' Association spent the final day of this week's general managers meetings gathering information about three major rule changes to bring back to its constituency.

The NHLPA was presented with three potential rule changes that could be implemented starting with the 2015-16 season: 3-on-3 overtime, coach's challenges and a new face-off rule that would require the defensive player to put his stick on the ice first during face-offs, including those in the neutral zone.