Thielen was upset over what he considered to be "cheap" tactics by the Patriots during the 24-10 win on Sunday at Gillette Stadium in Foxborough, Mass.
The Vikings had the ball and officials ruled that Latavius Murray had gained the yardage necessary to earn a first down with 9:02 remaining in the game. After the play, Patriots defensive back Patrick Chung crashed to the ground, signaling an injury.
Thielen said he thought it was "interesting timing" for the injury, which enabled the Patriots to have extra time to look at the play and consider challenging the ruling.
Microphones picked up Thielen shouting "that's bullcrap" in the direction of Belichick. The Patriots coach pulled the red flag out of his sock and threw it on the field for a challenge. Belichick then shouted what appeared to be an obscenity at Thielen. The wide receiver was later escorted away from the Patriots' sideline.
"I just thought the play was cheap," Thielen told reporters.
"I wasn't directing it toward him. I just thought the play was cheap, but like I said, I let the emotions get the best of me because it's a smart football play if you are in that situation. Why not? It's not cheating because there's no rule against it from a guy going down. I don't know if he was hurt or not. He might have been hurt. That's fine. It is what it is. But like I said, just interesting timing for a guy to go down when it's a close play."
The Patriots lost the challenge. Thielen told reporters that he did not take offense to Belichick's response.
Belichick was asked if the two were exchanging holiday greetings during the sequence.
"Yeah, pretty much," the coach said.