Lucas has thanked Liverpool's "special" supporters after completing his permanent transfer to Lazio.
The Brazilian has finalised a £5m move to Serie A, ending an Anfield association stretching back more than 10 years.
Signed by Rafa Benitez in 2007, Lucas made 346 appearances for Liverpool, won the League Cup in 2012 and was the club's longest-serving player.
He told the Reds' website: "Liverpool as a club and Liverpool as a city is a unique place. I think it's different from everywhere.
"The fans are a big part of the club, probably the most important part of the club, and without them Liverpool wouldn't be the same club I would say.
"Thank you for all the support, especially in difficult times, that's when it means a lot. We all know that Liverpool fans are really special and they were always here for me.
"I'll always be watching and supporting Liverpool and for sure I'll be back, in the city to visit friends and watch games in the future."