By Drazen Jorgic

RIO DE JANEIRO, (Reuters) - Former world No. 1 Ana Ivanovic exited the Olympic Games in the first round on Saturday, though the Serb refused to blame the wind or soaring temperatures that some players said were making it tricky to play in Rio.

Ivanovic went one set up against world No. 12 Carla Suarez Navarro before losing the next two error-strewn sets to the Spaniard. Ivanovic lost 2-6 6-1 6-2.

"It was a tough draw for the first round," said Ivanovic, the former French Open winner currently ranked as world No. 26.

"I had a chance to come back in the third set but every time I came close to pegging her back, I missed the opportunity," she added.

Ivanovic's match, like all the others on center court, was played in a stadium that was more than half empty, something likely to disappoint organizers.

But the size of crowds didn't bother Japan's Kei Nishikori, who opened the men's singles tennis tournament on center court by knocking out Spain's Albert Ramos-Viñolas with ease, winning 6-2 6-4 in two sets.

Nishikori said he didn't care if stadium was full or empty as long he kept winning. "That’s the most important (thing)," he added.

Though one issue that impacted Nishikori's contest and most of the matches on a hot and humid day was wind, with breeze drifting across from the ocean making conditions tricky.

"Here it’s very difficult to play because it’s fairly open, there is constantly some kind of wind," said Croatia's Marin Cilic, who beat Bulgaria's Grigor Dimitrov 6-1 6-4.

One person who thrived in the Rio sun was Australia's John Millman, becoming the first Olympian ever to win a men's singles match without losing a game.

Millman's "double-bagel" 6-0, 6-0, victory against Lithuania's Ricardas Berankis came after several shoulder surgeries that threatened his career. The Australian also took part in the late-night opening ceremony, which many other Olympians competing early on Saturday skipped.

"I couldn't miss the (parade). That was a really stirring moment for me. It's hard to explain the emotions I got walking into that stadium, and obviously that carried over to today," said Millman, 27.

"I was pumped up from the word go."

(Reporting by Drazen Jorgic; Editing by Tom Brown)