Firkser left Monday's practice session due to a leg injury, Tim Twentyman of the Lions' official site reports.
Firkser signed with the Lions on Friday to compete for a spot in the tight-end room in the wake of Tyler Conklin's (knee) injury. Firkser now appears to have picked up an injury of his own, and the severity of the issue will likely determine if he can make a push to garner a spot on the team's 2026 roster.