Second-seeded Viktor Troicki of Serbia and third-seeded Guillermo Garcia-Lopez of Spain were ousted from the Serbia Open in the second round on Thursday.
Troicki was broken eight times while losing to Marcel Granollers of Spain 6-2, 6-3, while Garcia-Lopez was beaten by Somdev Devvarman of India 7-6 (6), 2-6, 7-6 (8).
Granollers unraveled Troicki with drop shots that sent the Serb flying over the court to reach them. Troicki complained of back pain in the first set.
Granollers has also reached the semifinals in the doubles playing with another Serb, Nenad Zimonjic.
"I can win a lot of points in both singles and doubles," Granollers said. "I like this tournament, I was here last year, too."
Granollers will face Italy's Filippo Volandri, who reached his first quarter finals since February 2008 by defeating Illya Marchenko from Ukraine 6-3, 1-6, 6-3.
Garcia-Lopez struggled with his serve against Devvarman in the occasional drizzle. The Spaniard double-faulted six times and was broken six times. Devvarman sealed the victory after 3 hours, 14 minutes when Garcia-Lopez netted an overhead smash.
Devvarman will face seventh-seeded Janko Tipsarevic, who cruised to victory in his hometown event against Mischa Zverev from Germany 6-2, 6-0.
"I promised my audience they will see better play from me in the second round and I kept the promise," said Tipsarevic, who had to rally from a set down to beat Kei Nishikori of Japan in the first round.