Sir Alex Ferguson's side came from behind to win for the eighth time this season in all competitions after trailing 2-0 early in the second period. Hernandez was the inspiration after his half-time introduction, scoring twice and also seeing his shot deflect off Villa skipper Ron Vlaar for the other United goal.
But, although United's never say die qualities have not been in doubt, the Mexican is aware United have to stop conceding so many goals. He said: "Thankfully we got the three points. But we need to improve as well because we're conceding a lot of goals. We're very happy, we need to improve and this result is going to give us a lot of confidence."
Hernandez added: "The most important thing is that Manchester United are top of the league and after being 2-0 down that is a good result.
"We knew there was still plenty of time left and when we got one ... we knew we can get two or three goals each game. We knew once we got that chance it would come."
Defender Chris Smalling felt Hernandez reducing the arrears so quickly after Villa went two goals ahead was an important factor.
He said: "We managed to get that goal straight away and make an impact. We know we can play like that from the start. I don't know why we don't. It just took that kick up the backside to get us going, and luckily it paid off. We had to come out in the second half and put on a performance and luckily 'Chicha' (Hernandez) paid off with the goals.
"We knew there was still plenty of time left and that we can get two or three goals each game."
Hernandez has now scored seven times in the last five games and is back to the form he demonstrated in his first season at Old Trafford.
He said: "I have a lot of best (good) moments in this club and definitely this is one of them. To be honest in my mind I never think 'I need to change the game' only to do my best and the things the gaffer tells me to do."
Source: PA
Source: PA