Italy flyhalf Craig Gower announced on Wednesday that he will not take part in the World Cup (September 9 to October 23) as he has not fully recovered from a knee ligament injury.
The Bayonne player has been replaced in Italy's preliminary squad by Kristopher Burton.
"I'm not in a position to express myself 100 percent and I don't think I will be in the next few months," he said.
"It's not been an easy decision. Playing in a World Cup is the target of every player."
Australia-born Gower underwent surgery on his knee ligaments in November.
"The healing process has not gone as I expected and I don't feel capable of undergoing such high-level preparation without having returned to full fitness," he added.
Italy's South African coach Nick Mallett has named a squad of 36 players for a training camp beginning on July 3 in northern Italy's South Tyrol province.
He will then announce a 30-man squad for the World Cup in New Zealand ahead of two preparatory matches, against Japan in Cesena on August 13 and Scotland in Edinburgh on August 20.
Italy have been drawn in Group C at the World Cup, alongside Australia, Ireland, Russia and the United States.
Italy training squad:
Forwards: Lorenzo Cittadini (Treviso), Alberto De Marchi (Aironi), Salvatore Perugini (Aironi), Leonardo Ghiraldini (Treviso), Tommaso D'Apice (Rome), Fabio Ongaro (Aironi), Valerio Bernabo (Treviso), Joshua Furno (Aironi), Quintin Geldenhuys (Aironi), Cornelius Van Zyl (Treviso), Robert Julian Barbieri (Treviso), Mauro Bergamasco (Stade Francais/France), Paul Derbyshire (Treviso), Manoa Vosawai (Treviso), Alessandro Zanni (Treviso), Martin Castrogiovanni (Leicester/England), Andrea Lo Cicero (Racing-Metro/France), Marco Bortolami (Aironi), Carlo Antonio Del Fava (Aironi), Sergio Parisse (Stade Francais/France).
Backs: Pablo Canavosio (Aironi), Fabio Semenzato (Treviso), Riccardo Bocchino (Aironi), Tommaso Benvenuti (Treviso), Gonzalo Garcia (Treviso), Luke McLean (Treviso), Andrea Pratichetti (Treviso), Matteo Pratichetti (Aironi), Alberto Sgarbi (Treviso), Giulio Toniolatti (Aironi), Luciano Orquera (Brive/France), Edoardo Gori (Treviso), Kristopher Burton (Treviso), Mirco Bergamasco (Racing-Metro/France), Gonzalo Canale (Clermont/France), Andrea Masi (Racing-Metro/France).
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