Mitchell had surgery on his knee in the offseason and re-injured it during the lockout. He had been trying to rehabilitate his leg during the season, but ESPN's report states that Mitchell had arthroscopic surgery on the injured knee and will miss the remainder of the season.
The veteran blueliner had career-bests of five goals and 24 points in 76 games last season, and was a plus-7 in helping the Kings win the first Stanley Cup in franchise history.
We want to make sure that whoever makes our team really makes our team by earning it and not putting them in situations where they get preference because of their status as a first-round pick or whatever it might be. That's not going to happen. Everybody has to earn their way on our team.
— Columbus Blue Jackets general manager Jarmo Kekalainen on the team's prospects at development camp