Will Klein Bio
William Boone Klein, known professionally as Will Klein, is an American professional baseball pitcher for the Los Angeles Dodgers of Major League Baseball (MLB). He has previously played in MLB for the Kansas City Royals, Oakland Athletics, and Seattle Mariners. Klein made his professional debut in 2021 and earned a World Series championship ring as part of the Dodgers’ title run in 2025, highlighted by a memorable multi-inning relief performance during the Fall Classic.
Early Life and Background
William Boone Klein was born on November 28, 1999, and grew up in Bloomington, Indiana, where he attended Bloomington High School North. As a senior in 2017, he pitched only 17⅔ innings after breaking his thumb, but still struck out 30 batters and compiled a 1.98 earned run average. Despite that shortened showcase, Klein went unselected in the 2017 Major League Baseball draft and chose to continue his career at the collegiate level.
He enrolled at Eastern Illinois University to play college baseball for the Eastern Illinois Panthers, where he steadily developed across three seasons. Klein posted a 6.62 ERA over 17⅔ innings as a freshman and a 5.11 ERA over 24⅔ innings as a sophomore before lowering his ERA to 3.33 with 33 strikeouts as a junior in 2020, when the season was cut short by the COVID-19 pandemic. During the summer of 2019, between his sophomore and junior years, he also played collegiate summer baseball with the Lakeshore Chinooks of the Northwoods League.
Path to Professional Baseball
Klein’s draft stock rose following his junior year, and the Kansas City Royals selected him in the fifth round with the 135th overall pick of the 2020 Major League Baseball draft. He signed with the organization for $200,000, formally launching his professional career. That springboard into affiliated baseball marked the transition from college prospect to minor league pitcher in the Royals’ system.
Will Klein Career
Early Career (2021–2023)
Klein made his professional debut in 2021 with the Quad Cities River Bandits of the High-A Central, where he quickly established himself as a high-upside relief arm. Over 36 relief appearances, he went 7–1 with a 3.20 ERA, 121 strikeouts, and 44 walks across 70⅓ innings pitched, drawing organizational recognition as the Royals’ Pitching Prospect of the Year.
He missed the beginning of the 2022 season due to shin splints but returned in mid-May with the Northwest Arkansas Naturals of the Double-A Texas League, initially working as a starter before shifting back to the bullpen. In 2023, Klein returned to the Naturals before earning a mid-June promotion to the Omaha Storm Chasers of the Triple-A International League. He was also selected to represent the Royals at the 2023 All-Star Futures Game, and over 49 combined appearances he went 1–5 with a 4.62 ERA, 93 strikeouts, and 39 walks in 64⅓ innings.
Kansas City Royals (2024)
On November 14, 2023, the Royals added Klein to their 40-man roster to protect him from the Rule 5 draft, and he was optioned to Triple-A Omaha to begin the 2024 season. On April 25, 2024, Klein was promoted to the major leagues for the first time following an injury to pitcher Alec Marsh. In five appearances for Kansas City, he recorded a 6.35 ERA with six strikeouts across 5⅔ innings pitched before being traded later in the summer.
Oakland Athletics (2024–2025)
On July 30, 2024, the Royals traded Klein, along with Mason Barnett and Jared Dickey, to the Oakland Athletics in exchange for Lucas Erceg. With Oakland, he allowed five runs on two hits and four runs in 1⅔ innings pitched across three games. Klein was designated for assignment by the Athletics on January 17, 2025, ending his short stint in the Bay Area.
Seattle Mariners (2025)
On January 21, 2025, Klein was traded to the Seattle Mariners in exchange for international bonus pool space and was optioned to the Triple-A Tacoma Rainiers to begin the season. He struggled to a 7.17 ERA with 32 strikeouts and three saves over 22 appearances before being designated for assignment by the Mariners on May 31.
Los Angeles Dodgers Era (2025–Present)
On June 2, 2025, the Los Angeles Dodgers acquired Klein from the Mariners in exchange for Joe Jacques, giving him a fresh opportunity in a deep organization. He pitched in 14 games for the Dodgers, posting a 2.35 ERA in 15⅓ innings while also logging 22⅔ innings over 20 games for the Triple-A Oklahoma City Comets at a 5.16 ERA. After being inactive for the first three rounds of the postseason, Klein was added to the Dodgers’ active roster for the 2025 World Series.
His biggest moment came in Game 3 of the World Series, when the Dodgers’ bullpen was depleted and Klein delivered four scoreless innings, striking out five batters and earning the win after Los Angeles secured a walk-off victory in the bottom of the 18th inning. The appearance marked the longest of Klein’s major league career, surpassing his previous high of two innings in any single big-league outing, and helped the Dodgers capture the championship in seven games.
Notable Events and Milestones
Klein’s signature moment to date is his marathon relief performance in Game 3 of the 2025 World Series, a four-inning, five-strikeout effort that produced a win during an 18-inning Dodgers victory. That outing pushed him past his prior major league high of two innings in a single appearance and capped a season that ended with a World Series championship ring.
Will Klein Career Wins
Will Klein’s career wins to this point are anchored by a single but unforgettable major league decision: the Game 3 victory of the 2025 World Series. His professional track record also includes a 7-win minor league season in 2021 and steady contributions across High-A, Double-A, and Triple-A levels within the Royals system.
Major League Baseball Highlights
Klein’s most recent and only confirmed major league win came in Game 3 of the 2025 World Series, a marathon relief performance against a powerful National League opponent. Prior to that, his major league opportunities with the Royals, Athletics, and Mariners were limited and did not produce additional victories, though he posted a strong 2.35 ERA across 14 appearances for the Dodgers in 2025.
Will Klein Family
Personal Life
Verified public details about Will Klein’s personal and family life are limited at this stage of his career. He is recognized publicly by his full name, William Boone Klein, and continues to build his professional resume in Major League Baseball.
2025 Season Performance
The 2025 season was a whirlwind for Will Klein, beginning with a January trade to the Seattle Mariners and ending with a World Series ring in Los Angeles. After being designated for assignment by Seattle on May 31, he joined the Dodgers on June 2 and stabilized as a reliable relief option, posting a 2.35 ERA in 15⅓ innings across 14 appearances at the major league level. His Triple-A work with the Oklahoma City Comets showed more uneven results, with a 5.16 ERA over 22⅔ innings, but his big-league performance rebuilt confidence in his stuff.
Klein’s defining chapter of 2025 came in October, when he was added to the Dodgers’ active roster for the World Series after being inactive for the first three rounds of the postseason. In Game 3, with the bullpen stretched thin, he delivered four scoreless innings and struck out five to earn the win in an 18-inning thriller. The Dodgers ultimately closed out the series in seven games, giving Klein his first career World Series championship.