Lopez, Tomic out in Ecuador Open in Quito

Lopez, the Spanish second seed and last year's runner-up, was trailing countryman Albert Ramos-Vinolas 7-5 4-3 when he retired having called for the trainer numerous times.

Ramos-Vinolas progressed to the last four, with the official reasoning for Lopez's withdrawal listed as fatigue.

Awaiting Ramos-Vinolas in the semis of the clay-court tournament in Quito is defending champion Victor Estrella Burgos.

Estrella Burgos overcame Argentine qualifier Renzo Olivo 6-4 6-7 (5-7) 6-4 in two hours, 15 minutes.

Top seed Tomic was also sent packing as he went down to Italian Paolo Lorenzi 6-7 (5-7) 7-5 6-3.

The sixth-seeded Lorenzi served 25 aces and was not broken by the Australian.

Lorenzi will face Thomaz Bellucci after the Brazilian third seed battled past Pablo Carreno Busta 7-6 (7-0) 4-6 6-2.