Watch your back: Nadal withdraws from Madrid Virtual Pro charity match

While the Mutua Madrid Open Virtual Pro has replaced racquets with PlayStation 4 controllers, the innovative tournament is already shaping up to mirror a traditional tennis event.

On Sunday, after the ATP and WTA draws had been made, Gael Monfils pulled out due to streaming rights issues. He was replaced in his round robin group by an alternate, Benoit Paire.

Play opened Monday and unsurprisingly, forced all involved to be ready for anything. Technical difficulties acted like shower storms hitting Manolo Santana Stadium by interrupting play on multiple occasions. And soon, the injury bug struck the event's biggest draw, Rafael Nadal. At least we thought.

Tennis World Tour (Nacon Gaming)/Mutua Madrid Open Virtual Pro

After squeaking past Denis Shapovalov, 4-3 (3), to win his opener, Nadal was due to take part in a charity contest against YouTube star DjMaRiiO. Before long, tournament director Feliciano Lopez revealed the match would not take place as scheduled, as the 19-time major champion needed to rest his back.

"We had Rafa, but I think he had an issue on his back today," said Lopez. "I think he was a bit injured. He requested to play against DjMaRiiO tomorrow."

Luckily, with a flexible format to work with and believing everyone following the event could use a little humor, Lopez later clarified, "Guys, I was joking, of course."

Among the day's early winners included Murray, who defeated Paire, 3-1, and Diego Schwartzman, who posted wins over David Ferrer and John Isner. On the women's side, Belinda Bencic topped home favorite Carla Suarez Navarro, 3-1, and Fiona Ferro dismissed Karolina Pliskova, 3-0.