The wing-back is eagerly anticipating the Group C game against the titleholders, and feels their strong ties with the Catalan club make them the favourites once again
The core of Vicente del Bosque's squad consists of Blaugrana players, and Srna believes that this is a big advantage for the Roja.
"Spain are very strong because many of their players play at Barcelona, the best team in the world for the past five years, with the best coach," Srna was quoted as saying by Yahoo Eurosport.
"The best Spanish player I have played against in my career? There are a number of great players, but the best are Xavi and [Andres] Iniesta."
The Shakhtar Donetsk star then went on to praise Lionel Messi and Cristiano Ronaldo.
"Cristiano Ronaldo and Messi are best players of last 10 years. Especially Messi, who has become better than Diego Maradona, Marco van Basten, anyone really."
Croatia kick off their Euro 2012 campaign against Republic of Ireland on June 10.