Hernandez came on at halftime in the Community Shield and managed to score an unusual goal in the 3-1 win over Chelsea.
On Hernandez's goal, the Ferguson joked on Sky Sports: "He'll not try it again - it was a quite peculiar goal.
"But he's quick to get in the box - he's a really good finisher. He's got a bubbly character and speaks good English. He's settled in very well."