Spain playing Davis Cup tennis on clay in front of a home crowd is about as close to a sure thing as sport provides, and just because Rafael Nadal suddenly looks vulnerable the Czech Republic are not about to forget it.

Spain go into this weekend’s final as defending champions and with every reason to relish the prospect of a return to Barcelona’s Palau Sant Jordi, the indoor arena that played host to their first Davis Cup final win in 2000.

Nadal has been struggling of late, failing to win so much as a set in the ATP finals last week, but he and the rest of the Spanish team are such consummate performers on clay that to underestimate them would be unwise to say the least.

“We are outsiders in Barcelona,” Czech number one Radek Stepanek told newspaper Mlada Fronta Dnes.

“To take into consideration Nadal’s failure in London? That doesn’t work. The moment he steps on to the Barcelona clay, he will be a totally different player.”

Nadal, four times French Open champion, heads a formidable line-up that also includes world number nine Fernando Verdasco, David Ferrer (ranked 18th) and Feliciano Lopez (47).

Captain Albert Costa was part of the team that overcame Australia in a memorable tussle at the Palau in 2000, when huge crowds screamed themselves hoarse in support of their team.

It was clear watching Nadal in London that he has not yet recovered the magic formula of strength, skill and utter self-belief that made him such an irresistible force before tendonitis struck this season, keeping him out of Wimbledon and wrecking his chances of ending the year as world number one.

His uncle and coach Toni Nadal sparked further concerns when he said the world number two’s morale had slipped but the player himself is having none of that.

“My uncle has his opinion (but) my morale is fine, absolutely normal,” Nadal told reporters in Spain this week. “I’m delighted to be here going into this final with the intention of winning it.”

Along with Stepanek, the world number 12, the Czechs will pin their hopes on 20th-ranked Tomas Berdych, with Jan Hajek and Lukas Dlouhy also in the squad but unlikely to get on court.

As always in Davis Cup, the final will be decided on a best-of-five basis, with two singles rubbers on Friday followed by doubles on Saturday and the reverse singles on Sunday. Thursday’s draw will decide the order of the individual matches.

If Spain win they will become the first team to successfully defend the Davis Cup since Sweden in 1998.