"I don't think it's the worst-case scenario," Colts coach Frank Reich said after the game when asked about Castonzo's injury.
It's uncertain when Castonzo was injured because he completed the previous series without needing help from the training staff on the field.
The Colts entered Sunday depleted by injuries and COVID issues to their starting lineup. They were without defensive linemen DeForest Buckner (COVID-19) and Denico Autry (COVID-19), linebacker Bobby Okereke (ankle) and running back Jonathan Taylor (COVID-19).
Also Sunday, Colts linebacker Matthew Adams was ejected late in the first half after throwing a punch while playing on punt coverage.