Sir Alex feels Mark Clattenburg's decision to allow Nani's late goal against Tottenham to stand was the correct one.
Confusion reigned for the final few minutes of United's 2-0 victory at Old Trafford after the Portuguese winger had stolen in to poke the ball in to an empty net after Spurs stopper Heurelho Gomes had put the ball down believing his side had been awarded a free-kick. In actual fact, the ball was still in play after Clattenburg had waved play on following a penalty appeal and hand-ball from Nani.
Sir Alex admitted to being totally baffled by proceedings at the time, but having seen the replays and spoken to his players he feels the outcome was the correct one.
"At the time I had absolutely no idea what had happened!" the boss told MUTV. "We appealed for the penalty and didn't get it and as Nani fell the ball hit his hand and went into the goalkeeper's arms. At that point the goalkeeper's got control of the ball and the referee said to play on.
"The linesman didn't flag until after the goal was scored and I've still no idea why. The referee didn't blow his whistle at all and Nani actually looked at him to check. He said play on, so Nani put the ball in the net.
"The goalkeeper should know better. He's an experienced player and made a bit of a mess of it. You've got to play to the whistle, but he put the ball down thinking he was going to take a free-kick and, of course, it wasn't.
"The goal should definitely have stood because the referee has played on. It's the linesman and goalkeeper who have made the biggest mistakes."
Up until the controversy in the latter stages, it had been a closely fought game with Spurs, and Rafael van der Vaart in particular, causing more than a few scares for United's defence, especially in the first half.
"We gave him too much room and caused ourselves problems by doing that," said Sir Alex. "At the same time though, we played some good football and created some decent chances, but the game was probably too open.
"Once we got ahead we needed to make sure we didn't leave as much space as we had in the first half and we were far better in the second. Tactically and concentration-wise we did really well."