Mignolet, 25, has impressed with his confident handling and sharp distribution.
Lucas, 26, said: "We see on a daily basis that he is a top keeper. He works really hard and makes fantastic saves in training in every session and he is taking that into games. He's settled in quickly and we're just happy to have him here because he's a player who is getting better and better and we can see that he is playing with a lot of confidence.
"We have confidence that when called upon, Simon will make important saves - as he has done in so many games this season."
For breaking stories and all the great banter like us on Facebook: facebook.com/tribalfootball