Manchester City defender Michael Ball has been banned for three matches after admitting a Football Association charge of violent conduct.
Ball (right) later gave away a penalty by bringing down Ronaldo
Video evidence showed Ball stamping on Manchester United's Cristiano Ronaldo in City's loss to their derby rivals.
Ball told City's website: "I deeply regret what I did and have accepted the charge without hesitation. I have also sent a personal apology to Cristiano."
"My action should not be seen on a football pitch.
He added: "I know we have a responsibility at Premier League level to set a good example to the whole football community.
"I am proud of my disciplinary record and have never been sent off in my professional career."
Ronaldo converted a penalty to win the game for United - after he had been tripped by Ball.
In an eventful game for the 27-year-old, Ball went on to win a spot-kick for his team when Wes Brown was adjudged to have brought him down but Darius Vassell missed the chance to earn City a point.