Italy coach Cesare Prandelli has warned that his side's clash with Croatia on Thursday will be a "decisive match".
The Azzurri have not beaten Croatia since their neighbours from across the Adriatic gained independence from the former Yugoslavia in 1991.
"I've been saying for a while that Croatia is the most dangerous squad because it's the most unpredictable one," said Prandelli.
"This will be the decisive match of the group."
Prandelli may abandon the three-man defence for which he opted in Italy's 1-1 draw against Spain and revert to the four-man system that served him so well in qualifying - when his side conceded just twice in 10 matches.
Manchester City striker Mario Balotelli could also find his position in the team under threat from Antonio di Natale, who scored after coming on as a substitute in place of Balotelli against the world and European champions.
"What counts in the choices is the nervous and physical state of the players," said Prandelli.
"This will be the decisive match of the group. The idea is not to change too much, so that we have consistency."
Croatia know victory could seal their progress to the knockout stages, after they beat the Republic of Ireland 3-1 in their opening group game, and manager Slaven Bilic says his side fear nobody.
"One win would be enough to go to the quarter-finals," said Bilic. "We respect all of our opponents. We have no fear against anyone.
"Spain and Italy are favourites in our group, but I still think we are able to beat one of them."
Bilic, however, believes Italy should be regarded as one of the favourites to win the competition.
"You know how Spain are going to play but Italy are so unpredictable," he said.
"They can pass the ball, they can play the short balls and they can play through the middle.
"They can play counter-attack, with long ball from [Andrea] Pirlo to the strikers and they can play down the flanks.
"They are, for me, one of the biggest favourites in this tournament."