The Bavarians took the domestic and European titles last season, while also sealing the DFB-Pokal to complete a historic treble, never before done by a German club.
Gustavo left the Allianz Arena for Wolfsburg in the close-season, but will return on Saturday and took time to praise his former employers before going head-to-head.
He told Bayern's official website: "After winning the treble last season, Bayern are the best club in the world - you can be as definitive as that.
"So every opposing team will try and beat them. But they have so much quality, and if they pull together, they could do it all over again.
"It'll certainly be very different compared to a normal away game. I had two and a half seasons with Bayern, and now I'm back as a member of the opposing team.
"But it's also a very good feeling. We're playing against an extremely good team, and that's exactly what you want as a footballer. On top of that, I'll meet up again with a lot of the friends I made during my time with Bayern."
Gustavo turned down a move to Arsenal in order to seal his switch to the Volkswagen Arena and is looking forward to seeing friends, fellow Brazilians and former team-mates Dante and Rafinha on Saturday.
He added: "Those two will be very good friends for the rest of my life, and I met them in Munich.
"But it's not only them, it's also Franck Ribery, David Alaba and many others. We were always a very good group, the main reason why we were so successful."
