Switzerland's Davis Cup hopes were dealt a blow when top seed Stanislas Wawrinka pulled out of their World Group opening round tie with Spain with a knee injury.
The Swiss tennis association announced late on Thursday that Wawrinka had torn a ligament in his right knee during the team's final training session.
Wawrinka, who had been drawn to play Spain's world number 15 David Ferrer in the second singles rubber, will undergo an operation on Friday and is expected to be out of action for up to 12 weeks.
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The world number 32 was already carrying the weight of Swiss hopes following Roger Federer's decision to skip the competition's opening round.
As in previous Davis Cup campaigns, the world number one said he wanted to concentrate on his own flourishing tour career.
Spain have no such worries, with world number two Rafael Nadal lending his presence to an impressive, young squad.
Nadal is due to take on Swiss number three Marco Chiudinelli in Friday's opening rubber.
Following Wawrinka's withdrawal, Ferrer is now likely to face Davis Cup debutant Stephane Bohli, ranked 278th in the world.
The fourth member of the Swiss team, Yves Allegro, is a doubles specialist with no singles ranking.
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