The 24-year-old striker came to prominence in his first year at United, netting an impressive 20 times, but found his opportunities more limited last season as Danny Welbeck emerged as a first-team player.
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But Sir Alex believes a summer off, for the first time in several seasons, could bring the best out of the Mexican.
"I think this season we'll see a better Chicharito," he told Inside United.
"For the last four or five years he's played all through the summer. This year, with the co-operation of Mexico, he's had a proper rest.
"And that started right back in May when I decided not to take him to Belfast for the Harry Gregg testimonial.
"We wanted to give him as much rest as possible. He had a couple of weeks off and then joined the Mexico side for a couple of qualifying games before getting another few weeks' rest," he added.
"That was important for him and I'm sure he'll reap the benefits. We've already seen the fruits of that in the early training sessions and I think he'll have a top season.
"He's such a good professional and such a fantastic personality."
Chicharito featured in the 2010 World Cup as well as the 2011 Gold Cup for Mexico – both summer tournaments – but was allowed to skip the Olympic Games this summer.