PK Subban possesses the largest cap hit of any player on the roster and the third-highest AAV (first among defencemen) in the NHL for the upcoming season.
Data obtained from CapGeek*.
A public Google spreadsheet containing this cap info and the charts these visualizations are based upon is available here.
*This visualization does not currently include the $925 000 cap hit of Jiri Sekac. Therefore, the Canadiens are shown to have more cap space available here (~$3.6 million) than they are on CapGeek (~$2.7 million).