The Candiens have strong defensive depth in their organization, but many of their top defensemen prospects are either not ready to replace a player of Subban's caliber, or they're not ready to even play at the NHL level yet.
Nathan Beaulieu is one of the team's top prospects. He has many of the same offensive skills as Subban. He scored 52 points (11 goals, 41 assists) in 53 games last season for the Saint John Sea Dogs of the QMJHL, and he also racked up 100 PIM. He will be a fantastic NHL defenseman, but he's not a top pairing player yet.
Other impressive defenseman in the Canadiens organization include 2012 second-round pick Dalton Thrower and also Jarred Tinordi of the London Knights. But neither player is ready for the NHL yet. Both of these prospects are probably two years away.
The Canadiens have young defensemen who will be on the NHL roster in a few years, but none of them could replace what Subban currently gives the team at both ends of the ice.
Montreal needs Subban for the next two years at least, so signing him to a two-year deal wouldn't be such a bad idea.
Nicholas Goss is an NHL Lead Writer at Bleacher Report. He was also the organization's on-site reporter for the 2011 Stanley Cup Final in Boston. Follow him on Twitter.