The Fiorentina forward took to Twitter to voice his anger over suggestions he has been out of shape during training recently.
The 27-year-old missed much of the Serie A season due to a recurrence of a serious knee injury, yet still managed to score 16 goals in 21 league appearances for Vincenzo Montella's men in 2013-14.
The former Manchester United prospect had hoped to force his way into Cesare Prandelli's World Cup plans and was involved from the start in Saturday's friendly against the Republic of Ireland at Craven Cottage in London.
However, Prandelli opted to leave out Rossi at the expense of Mario Balotelli, Antonio Cassano, Alessio Cerci, Ciro Immobile and Lorenzo Insigne, and the striker has since hit out at suggestions he was dropped due to his unwillingness to compete physically against defenders.
"Everyone says out of shape: ask anyone the results from the tests during the week and the game," Rossi wrote on his official Twitter account Monday. "You will be suprised. Challenges? Fear?? What a joke…
"I get there thinking before the defender. Next time, as an amateur, I will wait for the defender to get kicked.
"Small details to which I hold. Now the most important thing, however, is to cheer Italy. Forza Italia! #quintastella."
Italy begins its World Cup campaign against England in Manaus on June 14.