Shun Yamaguchi (山口 俊)
- Bats Right, Throws Right
- Height 6' 2", Weight 198 lb.
- High School Yanagigaura High School
- Debut July 26, 2020
His father was sumo wrestler Taniarashi and Yamaguchi did some sumo wrestling in school.  He helped Japan win the 2005 Asian Junior Championship.  His fastball hit 94 mph in high school and the Yokohama BayStars took him in the 1st round of the 2005 NPB draft.  He had a rocky rookie campaign in 2006 (1-2, 6.43 in 5 G). In 2007, he was 0-3 with a 6.30 ERA. He moved to the bullpen in 2008 and made huge strides (1-1, 0.76 ERA, 28 K in 23 2/3 IP).
Yamaguchi was 5-4 with 18 saves and a 3.27 ERA in 2009, whiffing 68 in 55 innings. He was 6th in the Central League in saves. He remained Yokohama's closer for three years. In 2010, he was 2-8 with 30 saves and a 2.62 ERA, with 78 K in 68 2/3 IP. He was 3rd in saves behind Hitoki Iwase and Chang-yong Lim. He made the CL team for the 2010 NPB All-Star Games. He was again an All-Star in 2011, when he finished 2-6 with 34 saves and a 2.49 ERA in 59 games. He broke Hiroaki Nakayama's 23-year-old franchise record for games finished. He placed 4th in saves, between Dennis Sarfate and Lim. By this time, he was peaking at 98 mph on the radar gun.  He was again dominant in 2012 (1-2, 22 Sv, 1.74 in 60 G). He was 5th in saves, between Kyuji Fujikawa and Kam Mickolio.
His run of big campaigns ended in 2013 (5-2, 7 Sv, 5.40), and Jorge Sosa took over as closer. He spent most of 2014 in the starting rotation, his first time as a regular starter for Yokohama. He responded well at 8-5, 2.90 though he walked 60 in 124 innings. Had he qualified, he would have ranked 5th in ERA, between Yudai Ono and Toshiya Sugiuchi.  He was also 4th in free passes, though, between Shintaro Fujinami and Yasutomo Kubo. He slumped to 3-6, 4.49 in 2015 despite 119 K in 114 1/3 innings and cutting his walks to 42. He tied Minoru Iwata for 10th in the CL in strikeouts.
The Oita native had a strong campaign in 2016 at 11-5, 2.86. He just missed qualifying for the ERA lead; had he qualified, he would have been 5th, between Kazuto Taguchi and Yuta Iwasada. He was 4th in the league in wins, 10th with 121 K (between Taguchi and Ogawa), tied Tomoyuki Sugano for the most complete games (5) and led with three whitewashes. He became a free agent and signed with the Yomiuri Giants but was limited to four games in 2017 (1-1, 6.43) due to shoulder problems and a suspension after attacking a security guard, apparently while drunk. 
Back in health and scandal-free in 2018, he rebounded to 9-9, 3.68 with one save. He was 7th in ERA, between Messenger and David Buchanan. He was also 8th in wins, second to Sugano in complete games (10 to 6) and 5th with 144 K (between Messenger and Onelki Garcia). He had his best season yet as a starter in 2019, going 15-4 with a 2.91 ERA and 188 K in 137 IP, allowing 137 hits though he did walk 60. He tied Shota Imanaga for 3rd in the league in ERA, led in wins (two ahead of Imanaga), led in strikeouts (two more than Imanaga) but also led in walks (two more than Kris Johnson). He worked the 5th and 6th innings of 2019 NPB All-Star Game 1, replacing Imanaga and being succeeded by Scott McGough after getting roughed up for five hits including homers by Hideto Asamura and Hotaka Yamakawa.  He started the opener of the 2019 Japan Series and served up a two-run shot to Yurisbel Gracial in the 2nd; he allowed 3 runs in 6 to take the loss, with Scott Mathieson relieving him in the 7th. Yomiuri got swept by the Softbank Hawks and Yamaguchi did not appear again in the Series.  He made the Best Nine for the first time. He finished second in voting for the 2019 Central League Most Valuable Player Award, behind teammate Hayato Sakamoto. 
He made three starts for Japan in the 2019 Premier 12. Against Venezuela, he dueled Felix Doubront for three scoreless frames before allowing a run in the 4th; Taisuke Yamaoka relieved and Japan would rally to win, 8-4. He allowed two runs in four against Australia; Taguchi relieved with a 2-1 deficit and again Japan rallied after Yamaguchi left. He got the nod for the Gold Medal Game and struggled versus defending champion South Korea as Ha-seong Kim hit a two-run homer and Hyun-soo Kim a solo dinger in the first; Rei Takahashi took over in the 2nd and Japan's bullpen shut down South Korea the rest of the way. The comeback theme continued as Japan would win, 5-3. He tied Tim Atherton, Cody Ponce, Arturo Reyes and Hyeon-jong Yang for the most starts but had the highest ERA of that group. Only Yang allowed more hits in the tourney and he tied Yamaoka, Seung-ho Lee, Takayuki Kishi and Shairon Martis for the most runs allowed but he had the best ERA of that grouping. He tied Yi Chang, Enny Romero and Kwang-hyun Kim for 9th in the Premier 12 with 10 strikeouts. 
After the Premier 12, Yomiuri made Yamaguchi available through the posting system on December 3rd.  He was signed by the Toronto Blue Jays on December 17th to a two-year contract worth $6 million. He elected to wear uniform number 1 with Toronto, a number almost never worn by a pitcher. His debut in the major leagues was not a very good one. On July 26, 2020, he came on to pitch the bottom of the 10th against the Tampa Bay Rays after the Jays had taken a 5-4 lead in the top half by scoring their additional runner. However, with Kevan Smith starting the inning on second base as the Rays' additional runner, he was unable to retire anyone, first walking Jose Martinez on a full count, and then allowing both runners to score on a triple by Kevin Kiermaier to be charged with the 6-5 loss. His second appearance on July 29th was quite similar, as it also came in the 10th inning with an additional runner on base for the Washington Nationals. The Blue were considered the home team in the game, although it was played at Nationals Park, and Shun deepened his trouble by walking the bases loaded. He almost wiggled out of his own jam by striking out the next two batters, but Adam Eaton hit a ball that deflected off him towards 2B Cavan Biggio, but baserunner Andrew Stevenson managed to barely beat Biggio to the second base bag as a run scored. Asdrubal Cabrera then followed Kiermaier-like with a triple that cleared the bases, giving the Nationals an insurmountable 4-0 lead even if Shun retired the next batter. That gave him two losses in two appearances. He ended up making 17 appearances, all in relief, pitching 25 2/3 innings with a record of 2-4 and an ERA of 8.06. On the surface, this looked awful, but he was in fact quite useful to the Blue Jays in a thankless role, giving manager Charlie Montoyo the option to plug him in whenever he did not want to use one of his premium pitchers - or did not have options left - during a game. He was used in all sorts of situations, always ready to come into a game and get whatever number of outs were needed to spare others from having to pitch in a situation that was not optimal. The Blue Jays made it to the postseason, but he was not used in the loss to the Rays in the Wild Card Series.
- Alexis Brudnicki: "Yamaguchi 'really honoured' to join Blue Jays: Japanese righty brings reverse-slider-style 'shuuto' pitch, 'elite competitiveness' to Toronto", mlb.com, January 15, 2020. 
- Manny Randhawa: "Yomiuri Giants post RHP Yamaguchi", mlb.com, December 3, 2019.