The determination was made after Mitchell was reevaluated by the team's medical staff Tuesday. He will continue treatment in Salt Lake City instead of joining the team on its upcoming road trip and will be reevaluated before the beginning of the playoffs.
Mitchell, who averaged a career-high 26.4 points and 5.2 assists in 53 games this season, injured the ankle during an April 16 win over the Indiana Pacers. The Jazz have gone 8-5 in his absence to maintain the NBA's best record at 50-19.
Utah has a 1½-game lead over the Phoenix Suns entering Tuesday night in the fight for the Western Conference's top seed. The Jazz host the Portland Trail Blazers on Wednesday, before closing out the regular season on the road against the Oklahoma City Thunder on Friday and the Sacramento Kings on Sunday.
The Jazz also announced that All-Star point guard Mike Conley would sit out Wednesday's game. It will be the ninth consecutive game that Conley has missed because of right hamstring soreness.