Lamb is believed to be dealing with a "quad bruise" that is "not considered to be serious," Ian Rapoport of NFL Network reports.
Lamb was deemed questionable to return to Thursday's loss to the Buccaneers after -- per the Cowboys' official website -- taking a "hit on the same quad that got hit last week," and although he briefly got back out there he was not on the field for his team's final drive. Lamb does not appear to be facing an extended absence and will have extra time to rest and recover before the Cowboys face the Packers in Week 6, but it could be a few days until the next update on his status arrives.