The 22-year old Spaniard was lambasted by TV pundit Gary Neville after he failed to punch clear a late ball in last weekend's 1-1 draw with Tottenham, allowing Clint Dempsey to score an injury-time equaliser.
Neville suggested the United players would get on de Gea's back in the dressing room after the game but Banks feels that type of behaviour is a bit harsh for a young keeper.
"I was very upset to hear Gary Neville talking about how the players were disgusted with him (De Gea), how they were looking at him, after he hadn't punched the ball quite clear enough," he told Press Association Sport.
"I thought to myself, 'hang on a minute, it's not just the goalkeeper that makes mistakes, everybody makes mistakes in football matches'.
"He's got very good reflexes, makes excellent saves you think other goalkeepers probably wouldn't have got.
"He's got lots of years left yet. What he needs to do is to practice on the crosses as much as he possibly can.
"I used to practice on my weaker things as much as I possibly could and it certainly did help me.
"It's much more difficult for a goalkeeper playing in today's game. The ball is moving all over the place.
"For me, that ball has taken a lot of the art of goalkeeping out of the game. I do feel sorry for goalkeepers today."