Lane is listed as having an ankle injury, but Sweezy is the bigger concern because of a concussion. It's not known when the concussion occurred since Sweezy was not on the injury list Wednesday and participated fully in practice.
Any player who doesn't practice Thursday because of a concussion causes doubts about whether he will play that weekend. If Sweezy can't play Sunday, it's likely Paul McQuistan would start at right guard.
McQuistan has been splitting time at left guard with James Carpenter, who started the last two games. McQuistan started the first 12 games this season, including four at left guard and eight at left tackle when Russell Okung was injured. Sweezy has started all 14 games at right guard.