Hernandez flew out to the United States to join the club's pre-season tour, but he has so far only made two brief substitute appearances.
Even though new manager Louis van Gaal likes to play with two strikers, Hernandez still faces stiff competition from Robin van Persie, Wayne Rooney, Danny Welbeck and Wilfried Zaha for a first-team place.
In a rushed interview following United's penalty shoot-out win over Inter Milan on Tuesday night, Hernandez was asked if he saw his future at Old Trafford.
"The future, only God knows," he said.
When pressed on his limited match time under Van Gaal, the striker responded: "There is competition here and I will continue to work hard as I always do."
Hernandez was an instant hit at United following his surprise move from home-town club Guadalajara in 2011.
But the signing of Van Persie and the emergence of Welbeck has caused the Mexican to start just 15 Premier League games in the last two seasons.
Van Gaal was asked after the friendly win in Washington whether he would consider selling Hernandez.
He replied: "That I cannot answer because he is a player of Manchester United at this moment."
The latter part of the answer seemed to suggest Hernandez could be on his way out of United.
There are plenty of interested parties, chief among them Atletico.
The Spanish champions have already brought in forwards Mario Mandzukic and Antoine Griezmann this summer to compensate for the departures of Diego Costa, David Villa and Adrian Lopez, but Diego Simeone revealed he is still looking for an extra forward.
The Atletico coach thinks Hernandez would be an asset for his side.
"He's great in one-on-one situations and he's someone who could be useful to any team," the Atletico coach told a press conference in Mexico, ahead of his team's pre-season friendly with Club America.
"We are speaking to the sporting directors about the type of player we want and then it's up to them to bring the player in
With Javier Hernandez and lots of other great players, anything is possible
We can't close any door until the transfer window shuts."
Inter are also reported to be interested in Hernandez's signature.
Their defender Nemanja Vidic, who played alongside Hernandez at Old Trafford for three years, appears open to the idea of 'Chicharito' coming to Inter.
"He is a great player," Vidic said after Tuesday's game, which went to penalties after a goalless stalemate over 90 minutes.
"He is a Manchester United player but he can play in any team
He is a great professional
That is all I can say."
Source : PA
Source: PA