The 26-year-old is yet to start a game in Brazil this summer, but he came off the bench to add a third for Miguel Herrera’s side in their 3-1 win over Croatia as they secured progression from Group A.
That result saw Mexico end the group stages with seven points – only finishing behind favourites Brazil on goal difference – after seeing off Cameroon to win 1-0 and holding the hosts in a goalless draw.
Hernandez made just six Premier League starts last season as United slumped to a seventh-place finish and, as a result, his place in the Mexico side is no longer a given.
He said: "This whole year has been very tough. Players need confidence more than anything else, and I’ve been very short of it.
"Very few people have shown faith in me over this past year."
Mexico will now meet Holland in the last 16 as they look to make the quarter-finals for the first time since 1986, but Hernandez insists they are remaining grounded.
"We’re really happy, really pleased. We have to stay very calm, very humble and not get carried away.
"This is just one more step forward – a very important one – but just one more step.
"If we want to make history we have to beat Holland and keep moving along the path we’ve set out for ourselves."