Houllier said: "That does add a bit of pressure on him, but we are making sure he feels comfortable.
"He is settling well in the team and his team mates like him. It will take some games before he is working properly. I know he is a big player. He's a winner, a fighter and a creative talent.
"We have to be indulgent with Harry because he didn't have a good week of training before the game on Sunday.
"Don't forget he didn't play for his national team against Ireland and he only started training on Friday after an Achilles strain. As expected, he started the game at Villa Park slowly but got better and better and finished the game well.
"I was pleased with his contribution to the result. I'm not going to dwell on it. It happens that sometimes a player is not at his best because he didn't train due to an injury."