"He's been diagnosed with an elbow bruise," McCarthy said.
The coach said Favre aggravated an old shoulder injury.
"He was in for treatment today, and we see him playing (Dec. 9) against Oakland," said McCarthy.
Favre left Thursday night's 37-27 loss to Dallas in the second quarter after being hit on a Cowboys' blitz.
He has started 249 straight games at quarterback, an NFL record.