The pair picked up injuries in the win at Leicester Tigers last time out and forwards coach Phil Dowson revealed at Tuesday's media session that they are yet to train.
The Saints players were given last week off after beating Tigers and headed back to Franklin's Gardens this week to prepare for a home game against the Cherry and Whites.
But it remains to be seen whether Biggar and Mitchell can be involved in any sessions ahead of that crucial Gallagher Premiership match at Franklin's Gardens.
"Alex Mitchell and Dan Biggar are still a work in progress medically," Dowson said.
"Neither of them trained today but that doesn't mean they won't play this weekend.
"They are both with the medical staff and hopefully they'll be fit soon."
Teimana Harrison (hamstring), Ollie Sleightholme (back) and Ehren Painter (back) were forced to withdraw from the team to face Leicester.
And when asked whether that was more of a precautionary move, Dowson said: "It wasn't precautionary - they weren't fit to play.
"The boys have had a week off so those boys are back training, to what level it depends on how much contact and collision work they can do to make sure they're fit enough to face Gloucester.
"But if they don't make it, I thought the guys who stepped in at Leicester, Oisin Heffernan and JJ Tonks, did a cracking job."
But there is more concrete and upbeat news on centre Piers Francis who was forced off at half-time at Welford Road.
Francis had shoulder problems during the game but he happily gave an injury update at the media session.
"I've got ongoing management of my shoulder," Francis explained.
"A couple of times it wasn't where I wanted it to be, I felt a bit vulnerable and I didn't want to put the team in a bad position through my lack of ability with the shoulder.
"I was pleased to get to half-time and we made the decision that was best for the team.
"I was pleased to see the boys get the result and it's very cool."
Francis added: "I've got to be consistent with my management of my shoulder and I probably dropped off a bit in the week leading up to Leicester because it felt very good.
"I know I've got to be more consistent and I should be alright.
"It's feeling good now and the extra week we've had off has obviously helped so it's settled down now and I'm feeling strong again so there are no problems.
"It was nice to have a refresh week last week because the body was tired.
"We would have loved to be playing semi-final footy in the Challenge Cup last weekend but we're all guns firing for the Premiership now to give ourselves some play-off hopes."