Boston Bruins forward Seth Griffith will be out of action for three-to-four weeks with an MCL sprain in his left knee.
Griffith suffered the injury in the third period of Sunday's preseason win over the New Jersey Devils.
The Bruins open the regular season on Oct. 8 at home against the Winnipeg Jets.
The 22-year-old was a fifth-round pick of the Bruins in 2012.