Hazard left Lille for Chelsea in 2012 and has proved to be a big success at the capital club, most notably in 2015 when he was crowned the PFA player of the year.
But in an interview with French TV show Le Vestiaire, Mavuba has revealed how the Belgian international joined a number of Lille players who went out drinking the night before the club's final game of the season back in 2012.
"The night before games we usually did nothing, but were certain to finish third. We were playing against Nancy the next day, and it was Hazard's last game, so he prepared something small," the 32-year-old said, as quoted by the Metro on Sunday.
"In the morning, the coach (Rudi Garcia) went in Hazard's room and he hasn't been sleeping."
Hazard, 25, though went on to score a first half hat-trick after that. But Hazard was brought off in the 89th minute to a standing ovation which will have done little to ease his weary head.