The midfielder spoke to COPE and admitted the way in which his former teammate left wasn't the best.
Saul said, "The deal was moving along but it still surprised me.
"He was a very important player for Atletico Madrid and the fact he left makes it complicated for us. Atleti are bigger than any player and when he wore the shirt, no one could question him.
"I believe the way that he left wasn't the best but he doesn't need to be abused for it either."