The Reds are set to take on the Ligue 1 side in the Champions League group stages.
While they are top of the expanded group and in no danger of missing out on the round of 16, Slot is still hoping to continue their positive form in the competition.
He told reporters on Lille: “I’m impressed, not surprised but impressed. Not surprised because I think it was two or three years ago I played (against) the current manager when he was at Rennes, with my former club. Then, I was impressed by the way his team played. Yes, of course, a few weeks ago when I didn’t see them playing yet, I was like, ‘Oh, they beat Atletico Madrid, surprise; they beat Real Madrid, surprise.’ But now of course, I saw many games of them and now I’m definitely not surprised anymore but impressed, because they’ve deserved every single point they got until now.
“I just said something about the league table; for them it’s definitely not because they’ve faced easy competition. They faced Sporting Lisbon when (Ruben) Amorim was still there and Sporting Lisbon were impossible to beat. OK, they lost that one. But they faced them, they faced Juve, they faced Atletico Madrid, they faced Real Madrid. And now they are facing us and the next game is going to be difficult for them as well because then they face Feyenoord, my former club. So they haven’t been lucky with the fixtures they had, so that’s the reason why I’m so impressed with them in the Champions League. And an unbeaten run of 21 games probably tells you even more.
On Lille’s strengths, he added: “It is difficult for me to answer that question because many managers have changed their game plan against us compared to the games they have played before, in the last few months. But if I just look at how they’ve played in their last games and what their playing style is, I’m expecting an open game tomorrow because they are pressing every team, if it’s Olympique Marseille or Real Madrid or whatever team they face, they just press them high. They are not afraid to bring the ball out from the back.
“So, for us it’s going to be a change of styles compared to the recent teams we have faced, although Brentford also wanted to press us really high but also afterwards went to a real low block. But the three or four teams we faced before didn’t want to bring the ball out from the back. And that’s what Lille is doing, that’s what they are really good at, so that’s what I expect. But I expected that from a few teams we have faced in the last three or four games as well, but they changed their game plan against us. You have to ask their manager if he’s planning to play the same style or planning to change it!”