Zetterberg arrived at Joe Louis Arena on Tuesday morning with a brace on his left knee and got a ride to the dressing room on the back of a cart.
Third-seeded Detroit opens the playoffs Wednesday night at home against sixth-seeded Phoenix.
Zetterberg says he doesn't know if he'll play in Game 2 on Saturday. He was injured last Wednesday when he was checked by Bryan Allen in the 3-0 loss to the Carolina Hurricanes.
He missed the last two games of the regular season and finished with 80 points. That's 18 more than any teammate after averaging about 70 points the previous two years.
The Swede won the Conn Smythe Trophy as playoff MVP three years ago when Detroit hoisted the Stanley Cup.