Luis Milla's squad, which counts on the likes of Jordi Alba, Javi Martinez, David De Gea and Iker Muniain, are highly fancied to do well in London, but Mata is refusing to get carried away.
He said at a press conference: "It seems that we must win the gold without even playing first, and that's not the case. There are other very strong teams, who have squads that can challenge for the title.
"We have to be isolated from these expectations about winning.
"We want to do as well as possible, but we know that it will be difficult."
Mata, who was also part of the Spain squad that won the 2010 World Cup, added: "Spain have won in recent years because behind the success there is sacrifice and a lot of hard work, and this is a good path to follow.
"Personally I've had a fantastic season, and if we win, it would be a perfect summer and a first season in England in which I couldn't have asked for more."