Ferguson furious with Cole tackle
Hernandez was forced off due to injury in the second half of United's fifth straight win of the season after being on the wrong end of what Ferguson felt was a "shocking tackle" from the England full-back.
It is not known how long the Mexican will be sidelined for but Hernandez was in obvious pain as he hobbled down the tunnel and Ferguson was not impressed, telling MUTV: "It was a shocking tackle."
He added: "The referee booked him, so I don't understand why he hasn't given a penalty.
"Ashley Cole is very reckless at times. He is committed of course but being committed you can sometimes go over the edge a bit. That was an example of that."
Phil Dowd's decision to book Cole means that the matter is now dealt with, although television replays indicated the Chelsea man had been lucky to escape with only that sanction.
However, Fernando Torres will not be wanting to watch the game again after he followed up his second goal for the Blues with an embarrassing miss after rounding David de Gea but firing wide of an empty net nine minutes from the end.
Ferguson diplomatically labelled it "a bad miss" although Chelsea boss Andre Villas-Boas was even more sympathetic.
"You have to be fair," he said. "Two of the best strikers in the world missed crazy chances. It happened to Fernando and (Wayne) Rooney. It is nothing dramatic. Sometimes the ball goes in. It didn't fall our side.
"Normally it is 3-2. At that point it might have given us a mental edge for the last 10 minutes. We would have been completely exposed at the back but we would have taken the risk to try and get a draw. It didn't happen."
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