Thomas was ejected with 5 minutes, 43 seconds left in the Colts' preseason opener against the Seattle Seahawks when he lowered his head and made helmet-to-helmet contact with wide receiver David Moore on a deep incompletion.
NFL owners in March passed a rule that expanded penalties for contact involving helmets, including the potential for players to be ejected for lowering their heads to initiate contact with their helmets against an opponent.
"It was the appropriate call," Colts head coach Frank Reich said. "He should have been ejected. That should not be part of the game. That could have been avoided. Should have been avoided. The officials did the right thing."
Earlier in the game, Seahawks cornerback Akeem King drew a 15-yard penalty for lowering his head to initiate contact. Thomas' hit also drew a 15-yard penalty.
"I thought it was interesting in the first game, we were talking the whole time with the officials about the rules and about the hits and the helmet shots and stuff like that and trying to make some sense of it," Seahawks coach Pete Carroll said. "There was a couple of learning opportunities on this film in this game for everybody. They'll learn in New York, the officials will learn, the players and coaches will all learn as well.
"I'm really anxious to see what's going on around the league and all the instances that we can draw from. But all in all, the game was played hard by both teams and it didn't affect anything, I think, in terms of the outcome of the game. It's a real positive step forward. It's kind of a new era for us in ball. That was all right."
ESPN's Mike Wells contributed to this report.