Diaz had some weeks with the former Bayer Leverkusen star during Liverpool's preseason before being sold to Bayern.
Wirtz chose Liverpool over Bayern when leaving Bayer, but still spoke highly of his former suitor to Diaz.
"I was already familiar with the German league and know roughly what kind of football is played here," Diaz told local reporters.
"But yes, I had the opportunity to speak with Florian. The league is different from the English one, but it's also intense and physical. Football is also well played here, there are great teams, and the stadiums are always full.
"Florian also told me that the city is great and that I would really enjoy it here. He also wished me the best of luck. I'm very grateful to him."
