He is in contention to make his debut against Southampton tomorrow and Monreal revealed his fellow Spaniard has settled in well.
Monreal told the club's official website: "After having a few training sessions with him, I can say that I am very surprised with him.
"He is a very good player and he will fit into the group nicely.
"The language barrier is the first challenge a foreign player must face.
"Fortunately for Lucas, he speaks decent English and understands everything. The language barrier won't be an issue for him."