Michael Ballack will face no further action for his off-the-ball challenge on Patrice Evra during Sunday's Community Shield at Wembley.
Sir Alex Ferguson claimed Ballack should have been sent off for using an elbow to send Evra flying.
The incident provoked even more controversy because Chelsea took advantage of Evra's injury by racing to the other end of the field and scoring through Frank Lampard.
Referee Chris Foy was immediately besieged by angry United players, who pointed out the official had stopped the game a couple of minutes earlier when Ballack went down in similar circumstances.
As Foy did not intervene, it left the way open for the FA to take action. However, Foy has confirmed he saw the incident clearly and acted as he saw fit, leaving the FA to declare the matter closed.
Earlier, Ballack admitted he "blocked'' Evra and added he was "happy'' Foy did not blow for a foul.
Ballack declared: "I have to be happy that the referee didn't blow because maybe I blocked him a little bit. If the referee gives a foul it would have been okay as well, but he decided not to. It was a bit unlucky after that because they conceded the goal.
"I kept on playing but then I didn't have the ball so I couldn't see how injured he was.''
Ferguson also claimed Foy should have stopped play when Evra went down as the referee had done when Ballack was injured moments earlier, but Lampard said Chelsea had no case to answer.
Chelsea eventually won the game 4-1 on penalties after it finished 2-2 in normal time.
Lampard's strike put Chelsea 2-1 ahead in the 70th minute and when asked if he felt he should have kicked the ball out rather than trying to score, the England midfielder said: "I don't think any player would, you're entitled to shoot.
"That's what United did in the first half, but the referee stopped them and when Ballack went down in the second half they were complaining that they couldn't carry on.''