Heskey has started just one game in the Premier League for Villa this season and reports have suggested he could be on his way out of the club in January.
“Emile has to take the bull by the horns, for want of a better phrase,” O’Neill told the club’s official website.
“I want him to revert back to the things I know he is capable of doing, that made him a player Liverpool signed for big money.
“Things like getting the ball under control, using his strength and ability and being more selfish in front of goal.
“He was excellent at all those in the first place and he wants to get back to it. He still has those things in his game and deep down he would accept that.
“It will make him terrific for us and more potent for England. It’s my responsibility to get the best out of him. I felt when we signed him I could do this, but a day passes into two days, two days into a week and you need results.
“It has to be a two-way thing. He has to be encouraged, but more importantly Emile has to believe that what I am teaching him is correct. He knows what he has to do. He knows he is capable of doing it.”
