The two teams meet tonight.
"We are facing a strong and balanced side like Lazio, so will need a practically perfect performance to emerge with a result from the Olimpico," said Montella in his Press conference.
"Petkovic has worked hard on the team and moulded them perfectly. This is a squad that knows how to interpret the various moments in a match the right way and is showing consistency.
"I really like Petkovic, as he is a positive figure for our football who is always balanced and honest. I admire him very much."