Browns quarterback Duke Johnson Jr. is being evaluated for a potential concussion and could miss Sunday's season finale against the Pittsburgh Steelers.
Manziel complained of concussion-like symptoms when he arrived at the Browns facility in Berea on Wednesday. The Browns should have an answer about his status later in the day.
If Manziel is cleared, he will start Sunday against the Steelers. If he's placed in the concussion protocol, Austin Davis will make his second start of 2015.
Wide receiver Terrelle Pryor will take some snaps at quarterback behind Davis during today's practice, Browns coach Mike Pettine said. The team could also add a quarterback to the roster if Manziel is not cleared.
Additionally, veteran defensive back Tramon Williams was diagnosed with a concussion Tuesday. He'll be placed in the league's concussion protocol and likely won't be able to play in the finale.
Manziel took a couple of hard hits in last week's loss to the Chiefs, a game in which he ran for a Browns franchise record 108 yards.
If Manziel's 2015 season is over, he'll finish 129-for-223 with 1,500 yards, seven touchdowns and five interceptions in nine games (six starts). He also ran for 230 yards, the sixth-largest total by a Browns quarterback in franchise history. Manziel threw for a career-best 372 yards when the Browns lost to Pittsburgh in November.
Davis has appeared in two games, starting one since he signed with the Browns in September. He's 32-of-48 for 307 yards with a touchdown and an interception. The Browns lost, 37-3, in his start earlier this month against the Bengals.