Gaetano Berardi's horror tackle left studmarks down Callum McManaman's shin, Chris Coleman revealed.
The Leeds United skipper saw red in the final minutes of the 1-1 draw at Elland Road for a wild and late challenge on the Sunderland winger, with both feet in the air.
Paddy McNair played the ball out wide to McManaman on the right wing close to the dugouts, the wideman taking a touch before having his right leg wiped out by a flying Berardi.
Referee Jeremy Simpson didn't hesitate in showing the full-back a straight red and Coleman agreed with the decision, while also stressing Lynden Gooch was fortunate to come away without injury from an earlier challenge.
Coleman said: "That is a straight red. The one earlier on Lynden, if you don't jump out the way I dread to think.
"The Callum McManaman challenge is right down his shin from his knee to his ankle, he has studmarks.
"The kid got it wrong, the challenge. It was a straight red."
A draw was not enough for Sunderland, seven points from safety with only 15 points to play for but It was an entertaining game at Elland Road.
Both sides carved out enough chances to win the game, Leeds stopper Bailey Peacock-Farrell enjoying a man of the match performance including a stunning save to deny Ashley Fletcher's close range header.
Coleman said: "What a save from their keeper, point blank header, nothing wrong with that, it was an incredible save. He played well."
The Sunderland boss also had warm praise for his own keeper Lee Camp who has come under heavy fire this week after a poor display in the Easter Monday defeat to Sheffield Wednesday,
While the Cardiff City loanee still looked unconvincing on crosses into his area, Camp did make a number of good saves against Leeds including against Ronaldo Vieira and Samuel Saiz
Coleman added: "He was good and I was pleased for him. He has had his critics. We bought him in from Cardiff City in January for his experience.
"He was out injured a long time but has been in this situation before. He struggled to get up to speed with things at first but he is a great personality.
"When we have had a bad run he has been good with the players, he pulled off some good saves against Leeds."