A shin injury ruled the prolific forward out of Liverpool's last two games, a 2-1 defeat by champions Manchester United and a 1-1 UEFA Cup draw at Steaua Bucharest.
"It's a real boost," Houllier told reporters as he prepared for Saturday's premier league match. "His all-round game has improved and he's not just a goal scorer now. He frees up space for other players and he links up play with midfield well now."
"His presence is a boost for the confidence of the whole team and a threat for other teams."
Liverpool have a score to settle with Middlesbrough after a defeat at the Riverside last season heralded the start of a calamitous run of form that shattered their title hopes.
Houllier's league leaders had amassed 30 points in 12 games before their loss in the northeast triggered a series of 11 matches without a win, Liverpool's worst league run in 50 years.
"Maybe this time it will start us on a good run for the team," said Houllier, whose side are only eighth in the table, a full 13 points adrift of leaders Arsenal.
Houllier knows Liverpool have to sharpen up if they want to match the league's top sides, having lost by one goal to Chelsea, Arsenal and, a fortnight ago, United at home.
"I'm not looking for excuses but if we lose by the odd goal we have to learn and examine we have to do to get better."
"Maybe we have to be more clinical in our finishing and maybe more efficient and more clinical with our defending," said the Frenchman.
Liverpool have not kept a clean sheet in their last eight league games, prompting Houllier to add: "That is not like us. We have to keep the same attacking style and strengthen at the back."
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