OMNISPORT

Its Olympics inclusion questioned again, tennis showed why it belongs on any global sporting stage thanks to Novak Djokovic and Juan Martin del Potro.

An upset helps – and Djokovic's shock straight-sets loss in the first round at Rio 2016 on Sunday was just that – but the duo proved once more why the sport stays at the Games.

The rowdy crowd built the occasion and atmosphere as Del Potro claimed a 7-6 (7-4) 7-6 (7-2) win at the Olympic Tennis Centre.

A grueling two-setter, over almost two and a half hours, ended with a fortunate net cord and very warm embrace between friends.

It meant plenty to the Argentinean, who also sent world number one Djokovic packing in London, and the Serbian – who was crying as he left the court.

Golf can only be envious as top tennis players – namely Djokovic and Rafael Nadal – support their sport in such a way at the Games.

Tennis was at the Olympics at the inaugural 1896 Games, but disputes led to it being dropped, only to return in full – for good so far – in 1988.

Olympic gold is about all that's missing for 12-time grand-slam champion Djokovic, but the 29-year-old was almost powerless in his first-round loss.

Del Potro, the 2009 US Open champion still on the comeback trail after his career-threatening wrist injuries, was irresistible.

His forehand, one of the biggest weapons on the ATP World Tour, was crucial as he crunched 29 winners from that wing.

Djokovic made an incredible start to the year and was almost unstoppable, but, as it had to, his form has dipped since his maiden French Open success.

That still resulted in a title in Toronto, but it was an unconvincing one, and he was there for the taking, especially for a red-hot Del Potro.

A chanting football-like crowd created a spectacle, seemingly cheering for a third set just to see more tennis, with Del Potro's stunning forehands bringing them to their feet repeatedly.

Del Potro was also involved in the incredible match of London 2012, when he slugged it out for almost four and a half hours with Roger Federer in a semi-final at the All England Club.

Djokovic's departure just added to a remarkable opening two days of tennis, which has seen Venus Williams exit the singles and the doubles, the latter with dominant sister Serena.

Grand slams will remain the pinnacle, but as Djokovic and Del Potro showed, tennis matters at the Olympics.