What does it take to have a player's number retired?

Mats Sundin played for 3 Canadian NHL teams throughout the '90s and 2000s.  No wonder he never won a Cup.

Tomorrow night, the Toronto Maple Leafs will do something that they rarely do (no, not win the Stanley Cup...).  They will retire Mats Sundin's #13.  He'll join Ace Bailey and Bill Barilko as the only Maple Leafs to ever have their numbers retired by the club.  That got me wondering, what does it take to have a player's number retired?  Obviously, each team has a slightly different requirement to do the honor.  After hours (okay, minutes) of research, here's what I found.


Montreal Canadiens - Basically, if you're French-Canadian, scored a few goals, won a Cup, were really short or gave up 10 goals in a game, your number was retired.  Then there's Ken Dryden.  He was pretty good, though.


Toronto Maple Leafs - The Leafs have a tradition of only retiring numbers of Stanley Cup champion players.  Of course, after decades and decades of having nothing to do, they lifted that requirement for Mats Sundin.  Or maybe they're honoring his number.  There's a difference...


New Jersey Devils - It's pretty simple in New Jersey: if you're a defenseman and you win three Stanley Cups, your number gets retired.  That includes Martin Brodeur as a defenseman.


New York Rangers - Following New York sports tradition, if you were a fan favorite and didn't sign with your team's biggest rival, your number is automatically retired.


New York Islanders - The Isles also require a Stanley Cup for a player's number to be retired.  Or maybe they've just been so awful lately that there's been no numbers to retire...