A rest is something the striker had not experienced since arriving at Old Trafford due to various international tournaments, and with the Confederations Cup and the Gold Cup coming up in 2013 Ferguson thought it was essential that the youngster had time off.
The Red Devils manager suggested this led to Hernandez scoring a double in the 3-2 win over Braga.
"The thing that is making the difference is he got a proper rest in the summer," he told reporters.
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"He is such a dedicated footballer and professional in every training session.
"He's a really terrific player and the good thing is that he is still improving."
The 70-year-old now has a number of selection problems on his hands, as he has the likes of Danny Welbeck, Robin van Persie, Wayne Rooney and Chicharito all battling for two places up front. Yet praised his players' response to the situation.
"It's a good problem to have," he continued.
"I don't always enjoy it [telling players they're not playing] but it has to be done. In fairness to all the players they've accepted it well and adapted to it.
"I don't have any great problems other than having to tell one or two of them they're not playing."