GSTAAD, Switzerland, July 26 (UPI) --
Second-seeded Stanislas Wawrinka
of Switzerland was forced to retire from his quarterfinal match at the Swiss Open Friday when he injured his lower back.
Wawrinka was trailing No. 5 seed Feliciano Lopez of Spain 6-2, 2-6, 4-3 when he threw in the towel and send Lopez on to the semifinals.
Lopez will next face Robin Haase of Netherlands. Haase defeated 2011 Swiss Open champ Marcel Granollers of Spain 5-7, 6-3, 7-6 (7-5).
Sixth-seeded Mikhail Youzhny of Russia advanced with a 5-7, 6-4, 7-6 (9-7) win over fourth-seeded Juan Monaco of Argentina. Youzhny saved three match points to reach Swiss Open semis for the second time in three years.
Youzhny will face Victor Hanescu, who topped Daniel Brands of Germany 6-3, 6-4.
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