WATCH: Kei Nishikori receives roaring welcome at Atlanta Open on his return to the ATP Tour after 20 months

Kei Nishikori has officially returned to the ATP Tour after nearly 20 months away from professional tennis at the top level.

The Japanese star is competing at the 2023 Atlanta Open and faced Jordan Thompson of Australia in the first round on Tuesday. He received a thunderous welcome from the spectators at the Atlantic Station as he entered the court, and was given a guard of honor by the ball kids as well.

Nishikori came out on top in a two hours and 28 minute-long battle, getting the better of the World No. 63, 7-6(5), 7-6(5).

This was Nishikori's first tour-level match since the 2021 Indian Wells Open. Since then, he was on the sidelines due to a prolonged recovery period after hip surgery.

Nishikori only returned to professional tennis at the Palmas del Mar Challenger in Puerto Rico in June. His comeback plans were delayed multiple times earlier in 2023 due to unforeseen conditions. However, in Puerto Rico, the 33-year-old looked unbeatable and went on win the tournament, dropping only one set.

The former US Open finalist has gone on to play in two more Challenger tournaments in the US (Bloomfield Hills and Chicago) in preparation for the Atlanta Open. The former World No. 4 entered the main draw in Atlanta via protected ranking.

The ATP 250 tournament features World No. 9 Taylor Fritz as the top seed. 2022 Atlanta champion Alex de Minaur is also back to defend his title and is seeded No. 2. Other rising American stars, including Christopher Eubanks and Ben Shelton, are also in action in Atlanta.

Kei Nishikori thought about "retiring" while attempting to comeback to the ATP Tour

Kei Nishikori

While preparing to rejoin the ATP Tour, Kei Nishikori struggled mentally and admitted to battling severe depression. Currently ranked World No. 439, the Japanese briefly thought about retiring from the sport altogether while he could not even practice.

"I have been very depressed in the last few months. I even thought about retiring. From July to September, I was in rehabilitation at home. It's three months when I can't play tennis. I can't even take a racquet. Mentally, it's very complicated. Of course, I've been on the verge of retirement," Nishikori said in an interview late last year.

The 12-time ATP title winner had to undergo arthroscopic left hip surgery in January 2022. He disclosed that his hip bones required trimming during the procedure to relieve him of any pain.

"My bones have been deformed in hip and elbow, I needed surgery to trim the bones otherwise I feel pain, so (what happened) was inevitable. I never think about what I should have done (with these injuries), I know it's an unanswered question," he told Nikkan Sports.

Kei Nishikori will next face either qualifier Juncheng Shang of China or No. 6 seed Ben Shelton in the second round of the 2023 Atlanta Open. The Japanese previously played at the Atlanta Open in 2012, reaching the quarterfinals.