The Viola take on Udinese next Tuesday needing to overturn a 2-1 defeat from the opening leg if they are to book a place in the Coppa final.
Saturday's match at the Artemio Franchi stadium will be crucial with Fiorentina needing to keep up the pressure on Napoli, who are third and hold the last Champions League qualifying spot.
Last weekend's 1-0 defeat at Cagliari dropped fourth-place Fiorentina three points behind Napoli.
"We will try to turn around the tie on Tuesday," Montella said.
"Right now we are just focusing on Saturday's match.
"My players are really motivated for the game against Atalanta and this is a good sign.
"For us it is important to win but it is not going to be easy because Atalanta are in great form."
The Viola, who have won just one of their last four league games, will not be at full strength this weekend.
Fiorentina are without defender Nenad Tomovic and midfielders Massimo Ambrosini and Alberto Aquilani, all sidelined through injury.
Montella is expected to hand Juan Guillermo Cuadrado a start with the Colombian midfielder having rested on Tuesday.
Cuadrado will play in support of Alessandro Matri in attack.
German forward Mario Gomez, who returned to train this week after a five-month injury lay-off, is unlikely to feature on Saturday.
Rivals Atalanta enjoyed their biggest win of the campaign in last weekend's 3-0 triumph over Napoli.
The outcome, Atalanta's third win in their last four league games, lifted the Bergamaschi to 12th place, 10 points clear of the drop zone.
"We needed a perfect game to beat Napoli and my players delivered," Atalanta coach Stefano Colantuono said. "We are doing very well at home.
"However, if we depended on our away results, we would be second from bottom in the standings.
"We need to drastically improve our results away from home."
Atalanta have not come out triumphant on the road since beating Chievo in Verona on October 5.
The Bergamo outfit has collected one point since away from home.