The first-leg will be played in Iceland tonight.
"A game like this can hold dangers, as they are in excellent shape and unbeaten in six games, already going through three rounds," said Mazzarri in his Press conference.
"Their fitness levels will be superior to ours and we must be wary not to give them the opportunity to hit us. We must be cautious, as this is a dangerous team with quality players in attack.
"It's also important to remember that we have everything to lose, but we'll give everything we've got to ensure that doesn't happen."
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