Houllier said: "I think we need at least three players. Patrick Berger, Bernard Diomede and Vegard Heggam are all out of contract in the summer. Abel Xavier has already left the club. We will need to replace these players.
"If someone had said to us four years ago we would twice qualify for the Champions League and we would win six trophies, I don't think there would have been any complaints," Houllier insisted.
"For the last four years we have been competing for the Champions League spots. What I said yesterday still stands. There are some positives from this season and negatives.
"The positive is winning a cup final against Manchester United. Nobody will take that away from us. Also after a difficult period in the middle of the season, we managed to finish the season stronger.
"Our problems were at home. We conceded too many goals and we could have scored more. You expect a team that's developing and progressing to have fits and starts and that's what's happened.
"You must remember the average age of the team yesterday was just 24. I also think we paid because for half of the season we were without Stephane Henchoz."