The Mexican has complained to David Moyes about his lack of playing time and been told he can leave this summer, with Atletico Madrid interested in the striker.
Hernandez has spoken to United manager David Moyes on at least three occasions in the last two months over his frustration with a lack of playing time having made just five Premier League starts this season.
The Mexican has been told the club will listen to offers in the summer and feels he is no longer in Moyes' plans having fallen behind Wayne Rooney, Robin van Persie and Danny Welbeck in the pecking order at Old Trafford.
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Hernandez, 25, was particularly upset that he was overlooked for a clearly unfit Wayne Rooney in the second leg of United's Champions League quarterfinal defeat to Bayern Munich last week.
He had played for 90 minutes and scored in the 4-0 win over Newcastle four days earlier and felt he deserved to stay in the side, having also impressed in training in recent weeks.
Hernandez has made 31 appearances in all competitions this season - 20 as a substitute - and has scored nine goals during a disastrous first season for Moyes.
The former Guadalajara forward, who joined the club in 2010, is worried about a lack of sharpness going into the World Cup and looks set to join a summer exodus from Old Trafford.
Club captain Nemanja Vidic is heading to Inter while Rio Ferdinand, Patrice Evra, Shinji Kagawa, Nani, Anderson and Alex Buttner are among several other players expected to depart.