Legursky was hit in the side of his left calf by a falling Lions defender at the end of a run. He immediately grabbed for his left knee and was later carted off the field.
The Bills signed Legursky, 27, in June to compete for their open left-guard spot. Veteran Colin Brown looks to have that starting job locked up, but Legursky, who can also play center, was primed for the top interior backup spot.
Legursky has played in 50 career games (making 17 starts) over his first four NFL seasons, all with the Pittsburgh Steelers. He is the Bills' second-most-experienced offensive lineman, after right tackle Erik Pears.