The 25-year-old has been used mainly as a substitute by David Moyes this season, with only four of his 16 Premier League appearances coming from the start.
Hernandez has been heavily linked with a move away from Old Trafford in recent months, although the player’s agent insists he turned down offers from a number of European clubs during the January transfer window.
The Mexican still has two years remaining on his contract, although Herrera claims he has grown unhappy with his role at the club, after speaking to him on a recent tour of Europe.
“He seemed well but he is a bit frustrated because he doesn’t play despite training well and the truth is that when he does play, he makes a huge effort on the pitch,” Herrera told Raza Deportiva.
“He is a bit frustrated because the current manager doesn’t give him many chances, but he is committed and doing what he can to become a starter.
“He likes to work and likes to show determination to achieve his goal.”