Speaking to reporters, the Bayern boss said: "It's not a nostalgic return. I'm coming back as a coach, not a player. I don't want to bring in too much nostalgia, but it was great. I remember Sir Alex Ferguson was there to watch me. If I'd played well, maybe he would've made an offer for me.
"But I'm glad I ended up at the blue side of Manchester. As a player, you look forward to moments like this, no matter how tough they are. Celtic have a great home record, but that just increases our appetite for games like this."