Steven Gerrard has admitted that losing Lucas for much of last season was a big reason the for the team's disappointing league form.
Lucas was enjoying a bright spell at Anfield last campaign before suffering a season-ending knee injury in December.
Gerrard thinks that Lucas is integral to the club's success and is delighted to be back alongside the Brazilian in Liverpool's midfield.
The England captain told the club's official website: "Lucas's injury was a big factor on our season, because when he got the injury he was probably our best player, form-wise.
"He was playing superbly well, and he plays that position in the team where he does the ugly work, the work you don't really like to do: breaking up the play, protecting the back four, and when we lose the ball and teams counter-attack, he stops a lot of goals.
"It's great to have him back. He's a great person; he's great for the squad."
Gerrard and Lucas will both hope to be at the heart of the Reds' midfield when they begin their Premier League campaign against West Bromwich Albion on August 18.