Sources in Green Bay have revealed that Packers fourth-year CB-RS Will Blackmon suffered a season-ending ACL injury in the team’s Monday-night loss to the Vikings in Minnesota.

Blackmon, the team’s primary kickoff and punt returner, left the game after returning a second-quarter kickoff for 19 yards. The injury immediately appeared to be serious. Blackmon put no weight on the leg as he left the field with assistance from trainers after lying motionless on the ground for several minutes.

Although the team might seek outside reinforcements, it’s likely that second-year WR Jordy Nelson will replace Blackmon on both punt and kickoff returns, as he did against the Vikings on Monday night. Other possibilities currently on the depth chart include CB Tramon Williams and WR Brett Swain for punt returns and Williams and RB DeShawn Wynn for kickoff returns.