The Falcons ruled Neal out for the remainder of the game with an Achilles injury.
Late in the second quarter, Neal was covering Colts tight end Eric Ebron in the end zone. As Ebron ran his route, Neal stumbled to the ground and became visibly distraught.
Neal threw his helmet in frustration after he went down without contact, which prompted officials to flag him for unsportsmanlike conduct.
The 24-year-old defensive back was carted off the field after indicating to Falcons trainers that he suffered a lower leg injury. Neal previously sustained a season-ending ACL injury against the Philadelphia Eagles in 2018.
Kemal Ishmael and Sharrod Neasman are expected to fill in for Neal in his absence.