[5] The next week, he claimed his first ATP Challenger Tour title in Shanghai by beating Somdev Devvarman in the final.

[6] In September, Nishioka earned the men's singles gold medal in the 2014 Asian Games at Incheon, where he upset top seed Lu Yen-hsun of Chinese Taipei in the final.

He also became the first Japanese men's singles champion since Toshiro Sakai, who won the 1974 Asian Games in Tehran.

He followed that up with a straight-sets win over Marinko Matosevic to become the first teenage qualifier to reach the quarterfinals of the tournament since his countryman Kei Nishikori.

[citation needed] During the spring clay court season, Nishioka made his debut at the French Open, losing to fourth seed Tomáš Berdych in the first round.

[citation needed] In the 2015 US Open, Nishioka advanced to the second round of a Major for the first time in his career, beating fellow qualifier Paul-Henri Mathieu in five sets.

In November, he ended the 2015 season with his second challenger title in Toyota, beating Alexander Kudryavtsev in the final.

In February, he reached the quarterfinal of the Memphis Open as a qualifier, winning over Jared Donaldson and Illya Marchenko along the way.

[13] In June, Nishioka won through qualifying at Wimbledon for the first time, losing to Sergiy Stakhovsky in the first round of the main draw.

[14] The following week, he earned his third Challenger title in Winnetka without dropping a set, beating Frances Tiafoe in the final.

[15] At the Atlanta Tennis Championships, he reached his first ATP tournament semi-final, after defeating Daniel Evans,[16] fourth seed Alexandr Dolgopolov and Horacio Zeballos.

[18] At the Australian Open, Nishioka earned his second win at a Grand Slam tournament when he defeated Alex Bolt.

[22] In March, Nishioka built on his momentum by entering the main draw at Indian Wells as a lucky loser and reaching the fourth round, where he lost to world No.

[23] Nishioka's promising start to the season was abruptly cut short when he ruptured the ACL of his left knee in a match against Jack Sock at the Miami Open.

[26] At the Shenzhen Open, he won the first ATP World Tour title in his career, defeating Pierre-Hugues Herbert in the final.

[citation needed] At the 2020 US Open, Nishioka lost in the first round to former champion Andy Murray in a come-from-behind victory for the Scotsman in five sets.

[38] Getting past qualifying at the Adelaide International 2, he was defeated in the first round by lucky loser Thiago Monteiro.

[44] Making it past qualifying at the Abierto Mexicano Telcel in Acapulco, he upset seventh seed, world No.

[55] He defeated 16th seed Dan Evans in three sets to reach the semifinals of an ATP 500 event for the first time in his career.

He then won his second title, defeating fourth seed Denis Shapovalov in the final in straight sets.

[70] Seeded fifth at the Delray Beach Open, he defeated Oscar Otte before losing in the second round to Mackenzie McDonald.

[72] Seeded 29th at the BNP Paribas Open, he fell in his second-round match to qualifier Cristian Garín.

In June at the French Open,[78] he defeated qualifier Thiago Seyboth Wild, the conqueror of world No.

Due to a groin injury sustained during his match against Etcheverry,[81] Nishioka did not compete again until Wimbledon, where he lost in the first round to Daniel Galán.

[82] He reached his fifth final and first of the season at the Zhuhai Championships but lost to top seed Karen Khachanov.

[83][84] In July, Nishioka won his third title at the Atlanta Open, defeating Jordan Thompson and becoming the final champion at the tournament.

[85] At Japan Open where he entered the main draw as a wildcard, he upset Félix Auger-Aliassime saving two match points, reaching the second round for only the second time at his home tournament.