The 30-year-old goalkeeper has watched Mexes and Boumsong (pictured) come through the youth ranks to establish themselves as two of the best French youngsters around.
With Mexes just 20 and Boumsong only two years older, Cool thinks their progress has been phenomenal.
"The players in front of me are unbelievable," said Cool.
"They prove it every Saturday, and the most incredible thing is they are so good together.
"I was lucky to play with very good defenders at Auxerre, but this is the best matched defence I have ever had the pleasure to play behind."
