A big, bruising defender with a mean streak, Allen earned comparisons to Derian Hatcher at the time of his selection.

He was especially a standout on the penalty kill, logging heavy minutes as the Canucks finished near the top of the NHL in that category.

During the 2004–05 NHL lockout, Allen suited up for Khimik Voskresensk of the Russian Superleague (RSL) to stay in game shape.

On June 23, 2006, Allen was involved in a multi-player trade that sent him, Todd Bertuzzi and Alex Auld to the Florida Panthers in exchange for Roberto Luongo, Lukáš Krajíček and a sixth-round draft pick.

[2] On November 20, 2014 during the 2014–15 season, the final year of his contract, Allen was traded to the Montreal Canadiens in exchange for forward Rene Bourque.