David Luiz’s own goal and Robin van Persie’s close-range finish put the visitors in command after a breath-taking 12-minute period at Stamford Bridge.
However, Juan Mata’s superb free-kick gave Chelsea momentum ahead of the half-time break, and Ramires nodded Oscar’s cross past David De Gea in the 53rd minute to restore parity.
Chelsea duo Branislav Ivanović and Fernando Torres were both sent off in the space of six minutes before Javier Hernández netted United’s winner – replays showed the Mexican had retreated from an offside position to beat Petr Cech.
“Well the winning goal could have been offside so that’s a bit of luck,” said Ferguson.
“We started the game so well, we were absolutely brilliant. And then 10 minutes from half-time we lost our way a bit, I couldn’t wait for half-time.
“But they got that second goal just after the break, and from that moment, we had to start performing properly and we did better then.”
He added: “Oh yes, absolutely [the game could have gone either way at 2-2]. The sending off from the right-back was the turning point for us.
“We would have won it from that point, and of course we put Hernández on and he gets the winning goal for us. I think after that we had the momentum.”
In particular, Torres’ second yellow card prompted an angry reaction from Chelsea after the
Spaniard appeared to be clipped by Jonny Evans, but Ferguson felt the Blues striker was the architect of his own downfall.
“Well, did he intend to dive? He could have carried on running but he choose to go down.
“He could have carried on and scored that’s what I can’t understand. I would never have missed that chance o go through.
“He’s gone down when he could have continued, and he’s already been booked, so it’s his own fault.”
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