Manuel sprained the lateral collateral ligament in his right knee during the third quarter of the game. An MRI later revealed he will not need corrective surgery, but depending on recovery time, could miss up to six weeks.
"It's early on now to really give an exact time frame or even a window. What we need right now is for it to calm down and see where it's at," coach Doug Marrone said.
"Probably in a week see how it's progressing, see where he is, then get it down into a little bit more of a window."
In the meantime, the Bills are looking to add a replacement quarterback to their roster that could start in the game October 13 against the Cincinnati Bengals, and are rumored to be considering undrafted rookie Jeff Tuel.
"We will be looking to bring in another quarterback. We're in the process of that right now," Marrone said. "It's not a stretch [that the new quarterback starts against Cincinnati]. I think it all depends on who it is, what we get, what their background is in their system."