"There's two reasons. One is that Drew has had an excellent week of practice," Hufnagel told reporters Wednesday. "The other reason I will tell you when I'm done with my coaching career."
Calgary went 1-1 with Tate as the starter while Mitchell healed a sprained ankle and stretched ligament in his left leg.
After watching Mitchell practise Tuesday in wet conditions at McMahon Stadium, Hufnagel said "it looks good that he'll be playing the game," although the coach added he would wait another day before declaring his Friday starter.
Calgary (11-2) can secure a playoff berth with a win over the Roughriders (9-4). A loss by the Winnipeg Blue Bombers (6-7) to Ottawa in Friday's earlier game, however, would also ensure a playoff spot for the Stampeders.
Tate, 29, will get his third straight start this season. Meanwhile, the Roughriders announced Wednesday rookie Seth Doege will get the start Friday. The defending Grey Cup champions are also shuffling quarterbacks in the absence of injured veteran Darian Durant.
Doege split duties with Tino Sunseri in a 24-0 loss to the Edmonton Eskimos last week. Doege got on the field in the third quarter and was 5-for-11 in pass attempts for 61 yards. He threw one interception.
When Mitchell was injured in the fourth quarter Sept. 13, against Toronto, Tate completed a 40-33 comeback win going 6-for-6 in passing with a pair of touchdown throws and a two-point convert pass.
He completed 51 per cent of his passes for a combined 314 yards in his next two games. Tate rushed for a pair of touchdowns in a 31-15 loss to Montreal in Week 13.
Mitchell dressed as Calgary's third-stringer but didn't play in Saturday's 14-7 win over the B.C. Lions. Tate didn't throw a touchdown pass in the two games and was intercepted once.
"We have all the confidence in the world with Drew," Hufnagel said. "I do, the coaches do, his teammates do and he has a lot of confidence in himself."
Mitchell will dress for Friday's game, Hufnagel added.