Croatia currently find themselves second in the group after picking up four points from their first two games of Euro 2012, and are on the brink of qualifying for the quarter-finals.
"We have 23 lions in the squad," Srna told reporters. "We have no complex, no fear of Spain, we don't overly respect them.
"All the world will be watching and we've already shown that we can play with the big teams and win."
Croatia is the smallest nation at the tournament, with a population of just over four million, but Srna believes that the players' pride allows them to compete with the best.
"You look at Lionel Messi, he doesn't play so well for Argentina as he does for Barcelona, the same with Cristiano Ronaldo, he doesn't play so good for Portugal," Srna said.
"But Croatian players, we play much better for the national team than we do for our clubs. We are ready to fight."
Croatia coach Slaven Bilic has echoed his captain's comments. Bilic is due to leave his post after the tournament, but believes that the squad is in a good state.
"This current generation has something special," he added.
"The energy is perfect. We play our best when we play better against the best teams and this is the biggest match for this generation. It's going to be difficult against Spain but when we have the ball we'll attack with confidence.
"I think we'll have some surprises for the Spanish team."
Bilic has again played down talk of an arranged 2-2 draw between the sides, a result which would see them both qualify, regardless of scores elsewhere.
"I don't really want to waste any more words talking about it. Everyone in the competition and in Italy can be calm. It's a part of the brain that we don't have.
"If the final score is 2-2, that's it, it's football. If it's 7-7, then that would be strange."