The Mexico international spent the 2013/14 campaign on a season-long loan at Real Madrid after he was deemed surplus to requirements at Old Trafford.
Hernandez was linked with a possible move to bitter rivals Liverpool in the summer transfer window ahead of his return to the 20-time English champions.
However, United manager Van Gaal, who was appointed as David Moyes’s successor last year, has paved the way for Hernandez to salvage his Red Devils career.
“Javier can prove himself again and now [Radamel] Falcao and [Robin] van Persie are gone, his chances are better,” Van Gaal is quoted as saying by Daily Mail.
The 27-year-old striker scored nine goals in 33 games in all competitions for Carlo Ancelotti’s Madrid side last season.
Hernandez has netted 59 times in 154 games for the Red Devils following his move to Old Trafford from Guadalajara after the 2010 World Cup.
Van Gaal’s start their Premier League campaign with a home clash against Tottenham Hotspur.
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