Montella's men were held to a 1-1 draw by Torino in Serie A on Sunday as they slipped to fifth in the league table.
They host Tottenham at the Stadio Artemio Franchi on Thursday, having taken a 1-1 draw from White Hart Lane in the first leg.
Montella said he expected both teams to attack.
"It will be an open game against Tottenham on Thursday," he told Sky Sport Italia on Sunday.
"We want to give the best of ourselves as we did in the first leg."
Fiorentina were left to rue a penalty miss against Torino, with Khouma Babacar failing to convert a spot-kick in the 10th minute.
Montella said his team were shattered by their failure to collect three points.
"We're gutted, all of us. We kept pushing for the win right up until the end. It's a shame it ended the way it did," he said.
"We let ourselves get caught on the break too often and Torino were good at that."
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