Former striker, and now boss of the capital club, tells players to treat game as a decider for a place in Europe's elite competition but admits side will miss Phillipe Mexes
The capital club are six points behind fourth-placed Udinese, and Montella's side lost ground in the race for Europe last week when they tumbled against Juventus at home, losing 2-0.
But despite the collapse, the former striker is trying to inject hope.
"There are always less games to go and if we really want fourth place, which we do, then the game is decisive, it's a play-off," he told the press.
And his men will have to elevate their performance to deal with the threats they face at the Friuli.
He added: "Udinese are one of the best teams. They are young, they can run and have an infinite attacking line-up.
"For example they have [Alexis] Sanchez, who always gives a hand to his team-mates."
Philippe Mexes is missing after he underwent surgery to fix damaged ligaments in his knee this week following the injury he sustained against Juventus. And his lack of presence will be felt.
"We will miss him. He could have been very useful to us and I want to thank him for all that he has done here," said Montella, referring to Mexess' announcement that he will be leaving the club at the end of term.
Montella's future is also subject to investigation from Roma following the takeover by Thomas DiBenedetto.
"It's early to talk, there are many rumours," he concluded.
The following players have been picked for the squad:
Lobont, Castellini, Juan, Pizarro, Vucinic, Totti, Taddei, Loria, De Rossi, Riise, Perrotta, Borriello, Greco, Burdisso, Simplicio, Doni, Brighi, Pena, Caprari, Cassetti, Rosi.