The 28-year-old, whose only senior cap came in June 2011, has been in good form for Fiorentina since joining the Italian side from Villarreal in 2012.
"I honestly don't think about it anymore. The squad has now come together and is essentially closed," he told AS.
"I always play to give my best and, if I have the slightest chance then it would be great, but I think for me, it is almost impossible to play at the World Cup."
Valero has made 11 appearances for Fiorentina this season.