The English striker dragged his first half spot-kick just wide of the left-hand-post during an impressive performance at Old Trafford, where the Reds eventually sealed a surprisingly routine win over the Gunners in the Barclays Premier League.
Though the miss is a worry, Rooney told Sky Sports it will not play on his mind.
“I don’t know what happened but these things happen," he said. "Obviously, I am disappointed with the penalty but I will move on because we won the game and that is the most important thing. It’s something that is gone now for me.
“We had plenty of chances. Obviously, it was a poor penalty from myself but we should be taking care of games and we had a lot of chances late doors, especially when they went down to 10 men, to kill it off and we didn’t do it. That could cost us in the future. We need to make sure we are more clinical to finish games off.
“We tried to stop them playing," he added. "They are a fantastic football team but if you stop their playmakers then you have a chance, especially when you win the ball. If you win it high up the pitch you can break off them and create chances. We did that quite well and the led to a lot of chances for us. It certainly was our game-plan – to stop them playing and press them high.”
Victory over Arsenal during Saturday’s lunchtime kick-off saw United temporarily move ahead of Chelsea at the top of the league, capping an impressive week for the Reds following last weekend’s dramatic and entertaining 3-2 win at Stamford Bridge.