Former world number four Kei Nishikori won his first ATP Tour match in 19 months at the Atlanta Open on Tuesday.

The Japanese star was forced to undergo hip surgery at the end of 2021, resulting in nine months of rest and rehabilitation. Then on the cusp of making his return to the professional circuit late last year, Nishikori severely sprained an ankle, leading to another five months on the sidelines.

"Once or twice I almost thought [about retiring]," the 33-year-old told atptour.com.

"It was mentally shocking to be so close and then to have a second injury. I wasn't sure if I could come back from that. So that was the toughest time.

"One of my biggest doubts was whether I would be able to move like I used to. And also that you lose the feeling for the ball on the racquet and you have zero confidence. You™ve got to build again from zero, so it's a tough mental challenge."

Having slipped out of the top 400, Nishikori started slow. He took to the Challenger Tour to begin his comeback in June and promptly won his first event. A second-round exit and a quarter-final followed, after which he entered the Atlanta Open.

On Tuesday, he had to dig deep for two and half hours to earn a 7-6(5) 7-6(5) over world number 63 Jordan Thompson.

"It was very emotional after everything that it took to get back," said the 2014 US Open runner-up after the watershed win.

"I'm just so happy to be back here playing. I have zero pressure and can play free. I'm just having fun on the court. And I'm excited to be playing against the top guys again.

"I have had a good team around me and I'm very thankful that Max [Mirnyi] and Michael [Chang] kept encouraging me. They still believe in me and I believe it too."

But Nishikori has higher hopes and wants to test himself against the best. Since his injury-enforced hiatus in 2021, the likes of Carlos Alcaraz have picked up two grand slams and five Masters 1000 titles, while rising stars Holger Rune and Jannik Sinner have also forced their way into the top ten. These are the young pretenders Nishikori wants to measure up against.

"One thing I hope to get the chance to do is to play against these great young players like Alcaraz, Rune and Sinner at some point," he said.

"That's part of my motivation to try to play for a few more years. I don't think we have seen anyone like Alcaraz before. He looks like Rafa but he has more speed. Good defence, unbelievable forehand and he has a good backhand too."

Finished Ireland vs South Africa in United Arab Emirates T20I Series