He was finally given the chance to start the August 12 match against Softbank, and did not surrender any hits for 5.6 innings until the opponent's hitters managed to score a run that took away his first would-be win.

He got his first start on April 17 against Softbank in Koshien, and recorded his first career win after pitching 7 innings and surrendering only 3 hits and a single run.

[5] He caught the flu the day before his next outing, and assigning the newly acquired pitcher Evan MacLane as his replacement put an end to Orix's seven-game winning streak.

He was severely scolded for not taking better care of himself, and was removed from the roster by team manager Akinobu Okada as punishment.

[7] He then alternated as a starter and reliever in the following weeks, and on August 11, he pitched his first complete game while giving up only a single run.

He returned two months later and threw a no-hitter against the Softbank Hawks on October 8, fanning nine and allowing only one baserunner (a walk to Nobuhiko Matsunaka in the 5th).

[11] In game 3, he struck out four with one walk over two innings, and became part of a four-man combined effort to pitch a no-hitter against MLB all-stars who suffered their third straight loss.

[13] He returned to the mound on May 10 to notch his first victory of the season against the Fighters, a feat that he hasn't managed since he last won on August 1, 2014.

Despite giving away only 4 home runs and having the most wins amongst the team's pitchers, he also topped the league in losses with 12 and recorded a career worst of 48 walks.

2017 He started strong in 2017 where he went the distance against the Fighters on April 9, and threw a 154 pitch effort to record the season's first shutout win among all NPB hurlers.

[19] He returned in June, and gathered 4 more wins until his left wrist was hit and fractured by a batted liner during the August 22 game against the Fighters.

He pitched a lot of quality starts in succeeding games, but failed to get wins for lack of run support.

[22] He earned his domestic free agency option in May 2018, and according to media reports, he asked Orix about getting posted to the majors during the 2018 off-season but was turned down.

[23] After the season ended, he decided to exercise his option and met with Orix, Softbank and Hanshin who each offered him a four-year deal.

After many discussions with the said teams, he accepted the deal with Hanshin worth an estimated one billion yen even though Softbank offered double the amount.

[24][25] 2019 He was Hanshin's best pitcher in his first year with the club, winning 10 games with a 2.92 ERA (fifth-best in the Central League) and 1.13 WHIP in 172⅓ innings.

A 5'11 tall right-handed pitcher with three quarters delivery, Nishi throws a shuuto in the 140 km/h (87 mph) range as his main pitch, coupled with a slider and a changeup.

Despite being given what was considered a "death sentence" which could force the then 19 year-old rookie into early retirement, he decided to undergo treatment and was able to recover after 2 months.