Luka Doncic was labelled the "best player in the world" by Argentina coach Sergio Hernandez after he inspired Slovenia to an opening win at the Olympic Games.

The Dallas Mavericks star led his country to qualification for the Games and was at his remarkable best in Slovenia's 118-100 triumph.

Slovenia lead Group C after the first round of games, which wrapped up with Spain comfortably seeing off host nation Japan.

Ricky Rubio was the star for Spain, who emerged 88-77 victors at the Saitama Super Arena.


THERE'S NO DOUBT ANYMORE

Hernandez already had an extremely high opinion of Doncic, but his side's defeat at the hands of Slovenia's talisman left no question in his mind that he is the world's best.

Doncic scored 48 points, shooting 62 per cent from the field, and registered 11 rebounds in a stunning double-double performance.

Klemen Prepelic went four of six from deep in racking up 22 points, but this was predominantly a one-man show which left Hernandez in awe.

"It's really hard to analyse a game when one player just dominates everything as we saw tonight with Luka Doncic," Hernandez said.

"We tried everything that we could and it truly sounds like an excuse but we weren't able to do much when you have such a dominating player.

"I said this two years ago: he is the best player in the world, including the NBA. If there was any doubt in my mind, there is no doubt anymore that he is the best player in the world."

RUBIO PULLS THE STRINGS

Spain will have been boosted by the United States' defeat to France as they seek a first Olympic gold medal.

And it was Rubio who ensured their quest started in routine fashion, top-scoring with 20 points and excelling as a passer in registering nine assists.

Japan improved in the second half after scoring just 14 points in each of the first two quarters, NBA duo Rui Hachimura and Yuta Watanabe excelling for the hosts.

Hachimura scored 20 points while Watanabe finished with 19 points and eight rebounds but could not prevent Japan from coming up short in their comeback bid.