Geneva - US Open champion Marin Cilic has lost in the Geneva Open quarter-finals on Thursday, beaten 7-5, 6-3 by Santiago Giraldo of Colombia.
Cilic, who has been troubled by a shoulder injury this year, has advanced to only one tournament semi-final since winning his first Grand Slam title last September.
The second-seeded Croatian had nine aces on the clay-court surface but failed to create a break-point chance against the 67th-ranked Giraldo.
Giraldo will play Thomaz Bellucci of Brazil or Albert Ramos-Vinalos of Spain in an all-unseeded semi-final.
Top-seeded Stan Wawrinka of Switzerland was set to play Federico Delbonis of Australia in the final match on court on Thursday.
Results from the ATP Geneva Open on Thursday (x denotes seed):
Santiago Giraldo (COL) bt Marin Cilic (CRO x2) 7-5, 6-3