Biggar suffered a dead leg while skippering Wales to a 20-17 win against Scotland in Cardiff last weekend.
And though he would be available for his club this weekend as his country has a fallow weekend in the Six Nations, the 32-year-old's injury will prevent him from playing any part in the Gallagher Premiership clash.
"He's taken a bang on the quad and he's got a fairy significant dead leg," Saints boss Boyd said at Tuesday afternoon's media session.
"It's in the quad just above the knee and it's been a problem for him so he won't be available for selection at the weekend. He's been injured."
Saints are also set to be without flanker Tom Wood, who was forced off at half-time during the 35-20 defeat at Leicester Tigers last Friday.
"Woody's in Cardiff at the moment having a specialist appointment," Boyd said.
"We'll know more in 24 hours but it could be anything from fairly significant to not too significant.
"His shoulder popped out and it's just how much damage it did when it popped out.
"We hold our breath for Tom."
Powerhouse wing Taqele Naiyaravoro remains out due to the knee injury he suffered in a pre-season game at Bedford Blues back in September.
"He's still another couple of months away," Boyd said.
"He's coming along nicely but it's a long injury."
Full-back Tommy Freeman is still sidelined.
Boyd said: "He sustained a pretty substantial hamstring tear in an England training session so he's a good month away."
Another player still on the 'not available for selection' list is lock Alex Moon
"He had the wires removed from his finger the other day," Boyd said. "They couldn't find one of them so they had to open his finger up again.
"It's put him back another couple of weeks so he's probably another month away.
"We've had some unfortunate, longish-term injuries this season that you can't control, and he's one that's taking a bit of time."
But some good news comes in the form of centre Piers Francis, who has recovered from a foot injury sustained against Saracens at the start of January.
"He's been training so he's available for selection," Boyd said.