Arsenal manager Arsene Wenger was quick to issue an apology for the foul.
However, it is understood referee Alan Wiley at the time viewed the challenge as two players coming together, and so allowed play to continue, no separate disciplinary proceedings can be implemented, as the FA do not re-official matches.
Coyle was less than impressed by the challenge.
He said: "The second goal was the big turning point.
"Clearly it was a foul, and closer to a red card. It was akin to assault and it changed the game.
"However, the fact is the referee has not seen it, and the lad is prostrate on the ground, and Arsenal being full of fair play as we keep hearing, have carried on scored an equaliser. That is hard to take.
"I don't want to sit here and make excuses, but I have seen red cards for less."
Barclays Prem 2010-11 Win Outright: Arsenal 6/1