Italy coach Cesare Prendelli has admitted that his team "struggled like crazy" against Japan in hot and humid Recife.
Despite the "unbearable" conditions, the Azzurri sealed three points in a thrilling contest, which sees them progress to the semi-finals of the Confederations Cup.
However, the 55-year-old said that he is concerned ahead of the final Group A match against host nation Brazil.
"We deserved it against Mexico, but struggled like crazy tonight," Prandelli told reporters. "We were 2-0 down and in the first 25 minutes didn't know what we were meant to be doing. We got it back on track and then tried to preserve the result because we had run out of gas.
"We had no energy to do anything else at that stage. In those moments you are not clear-headed and struggling to do everything, so you have to be even more focused.
"I need to get the team back and then I don't know what performance we can put in against Brazil. The humidity and heat is unbearable, so we have to figure out how to deal with it."
The final group game takes place on in Salvador on Saturday.