The Blues meet LOSC in the Champions League tonight.
"We missed out on the title but qualified for the Champions League again, which was the goal when I arrived because Lille are a big club," he told chelseafc.com.
"Their new stadium is amazing, they have an incredible youth system and a fantastic training ground. The club is the real hub of the city so it's a great place to play football and I have fond memories from my time there.
"Ligue 1 is a strong league and I found it tough physically, as well as learning a lot tactically during my time there. Since I've left, the team have been a bit up and down. The French league is a different animal now and finishing second is almost like winning it because PSG are so strong."