The Chelsea playmaker was part of the Spanish squad that won the country's first ever World Cup in South Africa in 2010.
Speaking to Laureus.com, Mata said: "I think it's going to be really, really hard to win this tournament because obviously some of the countries that are going to be there are also really fighting to make it to the final.
"For me Brazil, the hosts, have a great, great squad with young players. They beat us in the Confederations Cup last summer. Italy too are going to really fight with us for the title."