Running back Mike Gillislee (knee) and linebacker Marquis Flowers (illness) returned from missing Wednesday's session while Mitchell sat out the team's first two practices of the week.
Mitchell is eligible to be activated to the roster at any point, but it must be done by Friday afternoon for him to play in Saturday's divisional round game versus the fifth-seeded Tennessee Titans at Gillette Stadium.
Coach Bill Belichick had a little fun at a reporter's expense when asked if he anticipated having the second-year wideout at any point during the postseason.
"I don't know," Belichick said. "I'll certainly let you know as soon as -- if that happens, we'll let you know as soon as possible. There won't be a second of delay."
Mitchell was placed on injured reserve prior to the Patriots' season-opening matchup with the Kansas City Chiefs. He was designated to return off injured reserve on Dec. 27, but was not activated as he deals with an unspecified injury.