The Buffalo News previously reported that McCarron received a hairline fracture in his collarbone during Friday’s preseason game against the Cleveland Browns.
McDermott said Sunday that McCarron did suffer an injury but that tests are “not totally conclusive” before acknowledging that the 27-year-old will go for another medical opinion.
The Bills’ quarterback competition will be trimmed to just rookie Josh Allen and Nathan Peterman should McCarron be sidelined for any length of time. The team returns to preseason game action next Sunday against the Cincinnati Bengals.
McCarron completed 3 of 6 passes for 12 yards before leaving Friday’s game against the Browns.
In four possessions with McCarron at quarterback, the Bills’ first-team offense gained just seven yards and failed to get a first down. He was sacked in the first quarter but stayed in the game until early in the second quarter.
Allen, who was the seventh overall pick of the 2018 NFL Draft, replaced McCarron and led the Bills’ first-team offense on an 80-yard touchdown drive in the second quarter.
While playing three possessions, Allen completed 9 of 13 passes for 60 yards and a 2-yard touchdown pass to wide receiver Rod Streater.
Allen was replaced in the third quarter by Peterman, who started the preseason opener before being replaced by McCarron in that game.
Peterman and McCarron have generally split the time with the first-team offense in practice.
McCarron signed a two-year, $10 million contract with Buffalo in March after four seasons with the Bengals.
He has played in 11 regular-season games, including three starts. All three of those starts came in 2015, and the Bengals had a 2-1 record in that span.
McCarron played in three games last season and completed 7 of 14 passes with no touchdowns and no interceptions.