Paul Lambert’s side surged into a commanding 2-0 lead courtesy of goals from Villa midfielder Andreas Weimann either side of the break to leave the home side on the brink of a memorable victory.
However, Hernández, who was a half-time substitute, finished from close-range in the 58th minute to offer the Red Devils hope, before his shot was turned past Brad Guzan by Ron Vlaar.
The Mexico international completed his brace and United’s comeback with a timely header beyond the Villa keeper after a superb Robin Van Persie free-kick.
“As I have been saying for the last few weeks, he’s fresh as he had a good summer break and it’s made a difference to him,” Ferguson told Sky Sports.
“When he came to us two years ago, that’s what we’re seeing again now and, when you score a hat-trick, you pick yourself. I think he’ll be playing next week.
“He does his natural thing. He’s fantastic in the penalty box with his movement, his quickness and being in space and that has got him three goals.
Ferguson also praised Lambert’s side for an impressive performance against the 19-time English champions, adding Villa were unfortunate to get nothing out of the game.
“It’s an absolutely magnificent result for us, it was a magnificent game, I must say that,” he added.
“Aston Villa played fantastic today, they’ve run their socks off and you have to feel sorry for them, with the effort they put in. But we never give in. We hit the bar twice.
“Once we lost the second goal, we came alive. It was a fantastic game.”
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