But Taqele Naiyaravoro may be in contention for the cinch Stadium at Franklin's Gardens clash, while Dan Biggar is available.
Proctor and Furbank both picked up injuries during the first half of the defeat at Wasps last time out.
Proctor came off early on with a hand injury, while Furbank was withdrawn at the break due to concussion.
And when asked for an update on the duo at Monday's pre-match media session, forwards coach Phil Dowson said: "Matty's had X-rays.
"They're currently waiting to see how bad it is.
"They're referring it to a specialist so it will be touch and go to see how bad it is.
"He's not a forward so I couldn't tell you much more than that!
"For Furbs, it was more than likely precautionary.
"I haven't checked up on Furbs or Matty really, I just asked how they were and they seemed fine.
"They've been in at the club but they haven't been training because they're still recovering from a hand knock and a head knock and they'll be moving on as it goes."
Biggar seemed to be struggling with a leg injury during the second half at Wasps.
But Dowson said: "He's in good form - he's flying around."
Naiyaravoro suffered a knee injury during a pre-season win at Bedford Blues last month and has not played since.
But Dowson said: "He's back in training.
"He's been released from the Covid bubble so he's back in and it's good to have him in the mix."
Piers Francis is another player who has yet to appear in competitive action this season.
The centre has been recovering from a shoulder problem.
"He has been training but whether he's in full training or not is open to debate," Dowson said.
"He's done some contact but I don't know whether he's done full contact protocol."