He told them he felt fine, that there were no side effects from the concussion he suffered a week earlier against Buffalo.
When Dr. Jerry Petty said no, Thomas was disappointed.
"Very, very surprised," he said Monday.
As down as Thomas was that he couldn't be a part of the 38-0 victory that coach Ron Rivera hopes is a catalyst for more wins, he's glad the league is taking such a hard stance on concussions to protect the long-term health of the players.
He's fortunate there are doctors thinking about him instead of what the coaches might want.
That the league reached a $765 million settlement over concussion-related brain injuries after more than 4,500 former NFL players filed suit has heightened awareness.
Thomas definitely paid attention.
"I mean, everything is for a good cause," Thomas said. "I understand the volume of what having a concussion is like. I don't take it lightly, and the NFL isn't taking it lightly. That's what you like the most, that they're taking the best interest for the players and not just themselves nowadays."
Thomas has been cleared to play this week against the Arizona Cardinals. He got it shortly after the Giants game.
Carolina (1-2) has gone from searching for enough players to fill the secondary to figuring out who might have to sit against the Cardinals (2-2) as safety Quintin Mikell (ankle) and defensive back D.J. Moore (knee) also are expected back.
"It's going to be an interesting week for us," Rivera said.
But it's a nice problem to have. And having players as selfless as Thomas has to make it a nicer problem.
"Because it's not about me," Thomas said. "It's about that 'W' we got in the last game."
The game may not have been about Thomas, but the decision to hold him out was all about Thomas. It wasn't that long ago that he would have been put back on the field without regard to his health.
"This game is built on entertainment and also safety," Thomas said. "You want to play the game the most safe way possible."