The Poland international said: "It's great to be back at this level and I'm looking forward to it.
"Remember it's not always the favourites who win the big tournaments. People talk about the Spartak Moscow game as one of my best nights in football. But getting to the Champions League Final would be my best.
"I think it's feasible for us to get to the final, why not? Who'd have thought a few years ago Greece would win the European Championships?
"No one expected that. Nobody expected Celtic to get to the last 16 of the Champions League last season.
"So anything can happen in football."