"He flew back to Paris with me on Monday and then on to Geneva to see a specialist, but we already had an idea as to what the problem was.
"We already had an idea what the problem was and he was rested against Birmingham but played against Auxerre and in the Worthington Cup final," said Houllier.
"He played through the pain barrier which, to me, embodies the spirit and resolve of the players here in this club.
"There is a risk if he doesn't have the operation now and plays on, he could damage his Achilles tendon."