The two South Americans have been a great success in Europe.
"He's a fantastic coach and has had great success everywhere, in Argentina, Chile and Spain," Pellegrini told a press conference.
"He always instills certain characteristics on his teams. Unfortunately, Athletic haven't had the best season this year, but they'll always be a dangerous rival who focuses on the attack, with strong determination to get a good result.
"I wish him all the best, and hope that after this match they can achieve some important wins."