Joe Hart and Gary Cahill warn England must expect the unexpected from Mario Balotelli in Manaus on Saturday.
Hart's former Manchester City team-mate was one of the inspirations behind Italy's run to the Euro 2012 final.
"You just never know with him," said England goalkeeper Hart.
Centre-half Cahill added: "Mario is an unpredictable player. I have played against him when he has done well, I have played against him when he has been brought off after 60 minutes."
Balotelli's place in the Italy team is by no means certain.
Ciro Immobile scored a hat-trick in the Azzurri's final warm-up game against Fluminense to give coach Cesare Prandelli a selection dilemma.
England are unbeaten in the 12 games that Cahill and Phil Jagielka have played together as a centre-back pairing.
They have also conceded just once in their last six outings, keeping three successive clean sheets.
"Rio Ferdinand and John Terry came out of the team at virtually the same time and left a big void," said Cahill. "There were a lot of questions asked - maybe there still are.
"Am I bothered? No. But I have really enjoyed playing with Phil. He is a fantastic player. Individually we know we are doing the right things."
If, as expected, Cahill starts against Italy on Saturday, it will mark his major tournament debut.
His hopes of making Roy Hodgson's squad for Euro 2012 were dashed when he suffered a double fracture of the jaw in a collision with Hart in the final pre-tournament friendly in Norway.
He did not make his debut until after the 2010 World Cup but now has 24 caps to his name.
"For me, it is huge," Cahill said. "The blow before the Euros, just before we were about to leave, was enormous.
"I have worked hard since then and hopefully I can play a big part this time. I feel confident and in a good place physically."
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