ESPN's Dianna Russini reported that Allen is in danger of missing several weeks due to the injury to his ulnar collateral ligament (UCL) that he sustained in Sunday's 20-13 loss to the Houston Texans. She also reported that Derek Anderson is expected to get the nod over Nathan Peterman to start versus the Colts.
Allen, who was the seventh overall pick of the 2018 NFL Draft, will have his MRI sent to Dr. James Andrews for a second opinion.
The 22-year-old Allen, who is listed at 6-foot-5 and 237 pounds, has completed 75-of-139 passes for 832 yards with two touchdowns and five interceptions this season.
Anderson signed with the Bills last week after spending several seasons backing up Cam Newton with the Carolina Panthers. The 35-year-old Anderson has played in 76 career NFL games with 47 starts (20-27 record) and his career completion percentage is an uninspiring 54.1 percent with 60 touchdowns, 60 interceptions and a passer rating of 71.1.
Peterman threw a 16-yard touchdown pass to Zay Jones in the fourth quarter on Sunday that put the Bills ahead 13-10.
After the Texans tied the game with a field goal, Peterman threw an interception that cornerback Johnathan Joseph returned for a touchdown.
Peterman then threw another interception, giving him nine picks in 79 career passing attempts. This season, Peterman has thrown two touchdown passes and five interceptions in 49 pass attempts.