Defeating Argentina in Davis Cup competition is a tall order under any circumstances, but the challenge will be even tougher than usual this week for Spain. The Argentines elected to play the final on an indoor hard court, the preferred surface of their two top guns, Juan Martin del Potro and David Nalbandian. Spain will have to try and stop their hosts despite a hostile partisan crowd, and without the services of such talents such as Nicolas Almagro and Tommy Robredo, or, of course, world No. 1 Rafael Nadal. To pull off the upset, Spain will need firepower from some unexpected sources. And they don’t come more unexpected, or anonymous, than Marcel Granollers.

A proficient dirtballer, Granollers has been battling in Challenger tournaments since 2005, with moderate success. His career highlight in this stretch came on, of all surfaces, grass, at the All England Club. In 2006, Granollers made his first Grand Slam appearance by qualifying for the main draw at Wimbledon. He would play Andrei Pavel gamely, but lost in straight sets, 6-7, 4-6, 4-6, in the opening round. By the end of 2007, the 22-year old from Barcelona had accumulated enough ranking points to be ranked No. 132 in the world.

Granollers’ play this season has signaled that he could soon be a fixture in the Top 100. He reached two finals at clay Challenger tournaments, winning in Tanger, Morocco, in March. A few weeks later at the U.S. Clay Court Championships in Houston, Granollers won his first ATP event, capping off the victory with a third-set comeback (from 0-3 down) against James Blake.

“It’s the best day of my life,” said Granollers after winning the title.

Since his victory in Houston, Granollers has risen to No. 56 in the world rankings despite somewhat spotty play. Given Spain’s considerable depth, it’s surprising that Granollers managed to parlay his recent play into a spot on the Davis Cup team. But injuries (Nadal) and declinations (Robredo et al) opened the door for Granollers, who eagerly accepted his federation’s invitation. And despite the fact that the unknown Spaniard has never before played Davis Cup, captain Emilio Sanchez-Vicario touted Granollers’ talent when announcing his team last Tuesday.

“Granollers has huge potential and a great future in front of him and is capable of playing singles and doubles,” Sanchez-Vicario said.  “It will be a great experience for him.”

At the moment, that experience will only entail spectating, as Granollers will start the tie on the sidelines. But last-minute substitutions are allowed in Davis Cup, so he could still participate in the action if Sanchez-Vicario decides to make a change.