Nick Kyrgios will continue his near four-year search for back-to-back singles wins after a promising but ultimately unsuccessful round of 16 defeat to Japan’s Sho Shimabukuro in Stuttgart overnight Thursday.

The Australian, 31, backed up a sparkling straight sets win against world number 36 Corentin Moutet in his return to the sport two days ago with another strong showing, winning the first set before falling 4-6 7-6 (7-5) 6-4.

All in all it was another encouraging display for a player who remains unranked after playing just seven singles matches since 2022.

Kyrgios was only broken once as his serve remains a weapon and the rest of his game should catch up the more he plays.

He again showed no signs of the knee and wrist injuries that have robbed the game of one of its most entertaining stars and delighted the crowd by using an underarm serve to draw an unforced error from his opponent to claim the first set.

Even his frustration, when the match began to turn against him, was handled with relative calm.

He scolded the chair umpire at 1-1 in the third set, claiming he should have been alerted it was the final game before new balls were being introduced.

There was a hint of petulance but none of the fury that has so often come in these moments.

After being challenged, the chair umpire responded: “I didn’t know you wanted to know.”

Kyrgios: “Isn’t that what’s supposed to happen?”

Umpire: “No, not really.”

Kyrgios: “Are you sure?”

Umpire: “Yes.”

Kyrgios: “I’m pretty sure it used to be a thing.”

Umpire: “I’ll let you know (next time).”

Kyrgios: “I don’t know if you’re new or anything, but (for) as long as I’ve been on tour, the game before, it’s been like ‘new balls next game’. Because that’s courtesy. You know how you hold us accountable, I think we should hold you accountable too, yeah?”

A Tennis Channel commentator gave a bemused laugh. “He’s just trying to fire himself up out there.

Ultimately Shimabukuro was the better player after the opening stanza, outplaying the Aussie in the breaker before claiming his first break of serve for the match in the ninth game of the decider.

The victory will see the 28-year-old break into the world top 100 for the first time and progress to his first ATP Tour quarterfinal.

“I’m really happy. Nick is a great player, and a big name in tennis,” he said. “It means a lot to win today.”

Kyrgios was scheduled to join fellow big-hitting drawcard Alexander Bublik in a doubles match later in the day.

His next singles action will come at the Halle Open in Germany next week, where he will continue to press his claims for a wildcard berth at Wimbledon.

“You always want to win, but maybe it’s no bad thing for him to just play a couple of matches,” Andy Murray’s former coach Miles Maclagan said in commentary for Sky Sports.

“Sometimes, if you’ve been out for a long time, and you play five matches in a row, it can be a big toll and your body isn’t ready for it.”

Originally published as Kyrgios scolds chair umpire over unwritten rule as his tennis comeback stalls