01/02/2012 10:10 EST | Updated 03/03/2012 05:12 EST

Edmonton Oilers centre Ryan Nugent-Hopkins leaves game with upper-body injury

CHICAGO - Ryan Nugent-Hopkins has left the Edmonton Oilers' game against the Chicago Blackhawks with an upper-body injury.

The Oilers announced the injury during the second period Monday night but it was unclear when it occurred.

The No. 1 overall pick in last year's draft, Nugent-Hopkins began the day leading NHL rookies with 35 points (13 goals, 22 assists).