Keylor Navas will be fit to face Spain in Wednesday's World Cup Group E opener, says Costa Rica assistant manager Ronald Gomez.

Paris Saint-Germain goalkeeper Navas has not featured for Christophe Galtier's side in Ligue 1 this season, acting as deputy to Italy's Gianluigi Donnarumma.

A lower-back issue for Navas raised fears the 35-year-old would not recover in time for Qatar, before Costa Rica's sole World Cup warm-up game scheduled for Thursday against Iran was cancelled.

The former Real Madrid keeper will still be capable of featuring against Spain, though, according to Luis Fernando Suarez's assistant Gomez.

"We already know all about Keylor Navas, we won't doubt him now as we know his capacity," Gomez said on Saturday. 

"He has had some pain in his back, but it is already solved, so we now expect him to play in the matches and offer what he has always given to us, which is reliability and good management of games."

The experienced Suarez will go to a third edition of FIFA's top competition with a different nation, but has come under some scrutiny for selecting 37-year-old Bryan Ruiz.

Gomez assured Ruiz was selected on merit, though, after doubts were cast on the choice to pick Costa Rica's second-most capped player.

"Everybody knows him. We all know what Bryan represents to this national team and our football history," Gomez added. 

"He is here deservedly, and the coach is right in selecting him here in order to [give him the chance to] retire from the national team, for whom he has given so much, because of the story he has had in our football and the international football star he has been.

"He deserves to be here, he's earned it, it is not a gift from our coach. He has the quality, although we will have to see how many minutes he is capable of playing. But for me, to bring Bryan here is perfect."

Suarez's side have won just two of their last 13 games at the World Cup (D5 L6) and are without victory in their last six at the tournament (D4 L2) – their longest winless run.

Yet, three of Costa Rica's five wins at the World Cup have come in their opening game, as they prepare to face Luis Enrique's talented Spain.