Miami, March 27 (IANS): Spanish tennis ace Rafael Nadal retired from his opening match at the Miami Open against Bosnian Damir Dzumhur after suffering from apparent heat exhaustion.

Nadal easily won the first set 6-2 on Saturday but began struggling with physical problems amid the hot, muggy conditions and called for medical assistance on two occasions, the first time after losing the second set 4-6 and again while trailing 0-2 in the decider, reports Efe.

He was finally unable to continue, feeling "dizzy" in stifling conditions, falling to the 94th-ranked Dzumhur 2-6, 6-4, 3-0 after an hour and 50 minutes.

Nadal's exit comes a day after Swiss legend Roger Federer withdrew from this hard-court tournament prior to his scheduled opening match on Friday against Argentina's Juan Martin del Potro.

Del Potro lost to the Swiss World No.3's replacement, Argentine Horacio Zeballos, 4-6, 4-6.

Dzumhur also called for a doctor at the end of the first set of Saturday's second-round match and complained that he had been feeling dizzy and had stomach problems, but he was able to recover.

The 29-year-old Nadal, who struggled through his worst season in a decade last year, was unable to build on his momentum from last week's event in Indian Wells, California, where he reached the semi-finals before losing to Serbian World No.1 Novak Djokovic.