The midfielder lauded the Belgian star's past contribution to the club's cause, citing how difficult it will be for anyone to come close to repeating such heights
The 21-year-old Belgium attacker departed Rudi Garcia's outfit earlier this summer in a massive €40.5 million move to the Champions League winners, and the former Villarreal man was quick to pay tribute to his old team-mate.
"Nobody can replace Hazard," Mavuba told L'Equipe. "We have lost a big player."
"That said, the force at Lille has always been a collective one, and since the transfer made both the club and Hazard a little more money, there was no choice.
"Salomon Kalou is a different type of player, but he will be an asset in helping us meet our objectives."
Hazard scored 20 goals in 38 Ligue 1 appearances last season, firing the Metropole side to third and subsequent Champions League play-off qualification.