Will Klein (baseball)

William Boone Klein is an American professional baseball pitcher for the Los Angeles Dodgers of Major League Baseball. He has previously played in MLB for the Kansas City Royals and Oakland Athletics.

Amateur career

Klein attended Bloomington High School North in Bloomington, Indiana. As a senior in 2017, he pitched only innings after breaking his thumb, but still struck out 30 batters and compiled a 1.98 earned run average. Unselected in the 2017 Major League Baseball draft, he enrolled at Eastern Illinois University to play college baseball for the Eastern Illinois Panthers. He posted a 6.62 ERA over innings as a freshman, a 5.11 ERA over innings as a sophomore, and a 3.33 ERA with 33 strikeouts as a junior in 2020 before the season was cancelled due to the COVID-19 pandemic.
In 2019, between his sophomore and junior years at EIU, he played collegiate summer baseball with the Lakeshore Chinooks of the Northwoods League.

Professional career

Klein was selected by the Kansas City Royals in the fifth round with the 135th overall pick of the 2020 Major League Baseball draft. He signed for $200,000.
Klein made his professional debut in 2021 with the Quad Cities River Bandits of the High-A Central. Over 36 relief appearances, he went 7–1 with a 3.20 ERA, 121 strikeouts, and 44 walks over innings pitched. MLB Pipeline named Klein the Royals' Pitching Prospect of the Year following the season's end. He missed the beginning of the 2022 season due to shin splints. He returned to play in mid-May with the Northwest Arkansas Naturals of the Double–A Texas League as a member of their starting rotation, but was later moved to the bullpen. Over thirty games, he went 1–1 with a 10.51 ERA, 55 strikeouts, and 51 walks over innings. He returned to the Naturals to open the 2023 season. In mid-June, he was promoted to the Omaha Storm Chasers of the Triple-A International League. He was selected to represent the Royals at the 2023 All-Star Futures Game. Over 49 appearances between Northwest Arkansas and Omaha, Klein went 1–5 with a 4.62 ERA, 93 strikeouts, and 39 walks over innings.
On November 14, 2023, the Royals added Klein to their 40-man roster to protect him from the Rule 5 draft. 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 Alec Marsh. In five appearances for Kansas City, he recorded a 6.35 ERA with six strikeouts across innings pitched.

Oakland Athletics

On July 30, 2024, the Royals traded Klein, Mason Barnett, and Jared Dickey to the Oakland Athletics in exchange for Lucas Erceg. He allowed five runs on two hits and four runs in innings pitched across three games. Klein was designated for assignment by the Athletics on January 17, 2025.

Seattle Mariners

On January 21, 2025, Klein was traded to the Seattle Mariners in exchange for international bonus pool space. He was optioned to the Triple-A Tacoma Rainiers to begin the season, where he struggled to a 7.17 ERA with 32 strikeouts and three saves over 22 appearances. On May 31, Klein was designated for assignment by the Mariners.

Los Angeles Dodgers

On June 2, 2025, the Los Angeles Dodgers acquired Klein from the Mariners in exchange for Joe Jacques. He pitched in 14 games for the Dodgers, with a 2.35 ERA in innings. In innings over 20 games for the Triple-A Oklahoma City Comets, he finished with 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. In Game 3, with the Dodgers' bullpen depleted, Klein struck out five batters across four scoreless innings and was credited with the win after the Dodgers secured a walk-off victory in the bottom of the 18th inning. The appearance was the longest of Klein's major league career; he had never pitched more than 2 innings in any major league game. The Dodgers won the series in seven games.