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SF Giants add hard-throwing former Phillies prospect from Frontier League

The SF Giants added some velocity to their organization earlier this week, acquiring former Phillies and Twins prospect Tanner Kiest from the Joliet Slammers.
Marc Delucchi|
SF Giants add hard-throwing former Phillies prospect from Frontier League
SF Giants add hard-throwing former Phillies prospect from Frontier League

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The SF Giants added a hard-throwing right-handed pitcher with a winding baseball story. The Giants acquired pitcher Tanner Kiest from the Joliet Slammers of the Frontier League on Tuesday, per the Slammers Twitter. Kiest has previously been a prospect in the Philadelphia Phillies and Minnesota Twins organizations but has not played with an MLB affiliate since 2018. Instead, Kiest has traveled across North America between stints in various independent leagues.

Kiest was a 28th-round pick by the Phillies all the way back in the 2014 MLB Draft out of Chaffey Junior College in Southern California. Kiest made 21 appearances at the Arizona Rookie League between 2014 and 2015, striking out 24 in 25 innings pitched with 33 walks and a 5.76 ERA before he was released in August of 2015.

So began Kiest's journey across various independent leagues. Kiest played in four different leagues in 2016 and 2017 before signing a minor-league contract with the Twins prior to the 2018 season. Kiest was assigned to Minnesota's Single-A affiliate but continued to struggle with control. While he struck out 14 batters in 14.2 innings pitched (seven appearances), he issued 14 walks and recorded a 7.98 ERA. He was released in July of 2018 and was back in an independent league before the end of the year.

From 2019-2020, Kiest pitched in the American Association before joining the Frontier League in 2021, where he has played since. After posting a 6.53 ERA in 2021, the righty took a significant step forward in 2022. Kiest was clearly overpowering opposing hits, racking up 80 strikeouts and allowing just 30 hits in 49 innings pitched with 3.12 ERA. His walk rate remained higher than ideal (4.2 walks per nine innings pitched) but was far from unacceptable.

After an offseason stint in the Mexican League, Kiest was even better early this season. In six innings pitched (six appearances) with the Slammers, Kiest allowed two runs on four hits and two walks with 11 strikeouts. According to a tweet from his pitching coach, Wes Anderson, Kiest's fastball has reached 99.1 mph this season alongside a powerful slider that has reached 89.3 mph as well.

Now in the SF Giants organization, Tanner Kiest will have his third opportunity to prove he has the potential to be a future big leaguer in the minor leagues. Now 28, the Yucaipa, California native has travelled a long path back to affiliate ball and hopes he has made the necesarry strides to hit the ground running.

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Marc Delucchi
MARC DELUCCHI

Marc Delucchi (he/they/she) serves as the Managing Editor at Giants Baseball Insider, leading their SF Giants coverage. As a freelance journalist, he has previously covered the San Francisco Giants at Around the Foghorn and McCovey Chronicles. He also currently contributes to Niners Nation, Golden State of Mind, and Baseball Prospectus. He has previously been featured in several other publications, including SFGate, ProFootballRumors, Niners Wire, GrandStand Central, Call to the Pen, and Just Baseball. Over his journalistic career, Marc has conducted investigations into how one prep baseball player lost a college opportunity during the pandemic (Baseball Prospectus) and the rampant mistreatment of players at the University of Hawaii football program under former head coach Todd Graham (SFGate). He has also broken dozens of news stories around professional baseball, primarily around the SF Giants organization, including the draft signing of Kyle Harrison, injuries and promotions to top prospects like Heliot Ramos, and trade details in the Kris Bryant deal. Marc received a Bachelor's degree from Kenyon College with a major in economics and a minor in Spanish. During his time in college, he conducted a summer research project attempting to predict the future minor-league performance of NCAA hitters, worked as a data analyst for the school's Women's basketball team, and worked as a play-by-play announcer/color commentator for the basketball, baseball, softball, and soccer teams. He also worked as an amateur baseball scout with the Collegiate Baseball Scouting Network (later renamed Evolution Metrix), scouting high school and college players for three draft cycles. For tips and inquiries, feel free to reach out to Marc directly on Twitter or via email (delucchimarc@gmail.com).

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