The pair played together for Crystal Palace.
Wan-Bissaka said: "We're still in contact.
"When I saw the draw, I thought about it. I'm happy for him to go out there and he's playing well for them now. I think he's enjoying it. He'll just be looking forward to the competition in that different league and also in the Champions League.
"You know, even from when I was training with him at Palace, I respected him a lot. That was the battle we had. That helped me as a player as well.
"You just never know with him, on what day, and you have just got to be prepared. Obviously, you just play your own game and, all that comes, you deal with it then."