Italy midfielder Daniele De Rossi apologised for catching US striker Brian McBride with his elbow in Saturday's 1-1 draw in World Cup Group E.
"I spread my arms and caught him," the 22-year-old De Rossi told reporters after being sent off in the 28th minute for an incident which left McBride needing three stitches under his left eye.
"I'm sorry. I certainly didn't want to hurt him and didn't want to give him an elbow, and I'm sorry for my team mates."
His colleagues rallied round De Rossi, who may receive a lengthy suspension.
Captain Fabio Cannavaro said: "When someone makes a mistake, they realise it straight away.
"But we mustn't crucify anyone, we're a tightly knit group. A mistake has been made and we'll learn from it."
Defender Alessandro Nesta said: "I feel sorry for him, he's a good lad. It's not easy to play in the World Cup when you're just a lad.
"He was probably too wound up with all the responsibility and that was the reaction. We're behind him."
Italy lead the group by a point from Czech Republic and Ghana, with US bottom on one point.
"They [US] were certainly really fired up at the start and clearly very determined to get stuck in physically," said Alessandro Del Piero, a late Italian substitute.
"But they couldn't afford to slip up tonight. With the goals and the red cards, we've seen everything happen in this game."
Looking ahead to the final group game against the Czechs on June 22, Del Piero said: "We're top of the group and to get through to the next round we can take a win or a draw.
"Thursday will be like a final."