Ferguson split the 2016 season between the Low–A Spokane Indians and Single–A Hickory Crawdads. In 23 appearances, he combined for a 3.92 ERA and 56 strikeouts across 43+2⁄3 innings pitched.[3] Ferguson split 2017 between Hickory and the High–A Down East Wood Ducks, but struggled to a 2–6 record and 6.61 ERA with 57 strikeouts across 36 appearances.[4]
Ferguson once again played for Hickory and Down East in 2018, registering a 4.76 ERA with 14 strikeouts in 14 games. He was released by the Rangers organization on March 19, 2019.[5]
Trois-Rivières Aigles
On April 5, 2019, Ferguson signed with the Trois-Rivières Aigles of the Can-Am League.[6] In 45 outings for the Aigles, Ferguson compiled a 3–5 record and 4.75 ERA with 55 strikeouts across 55 innings of work.
Los Angeles Dodgers
On February 23, 2020, Ferguson signed a minor league contract with the Los Angeles Dodgers. He did not play in a game in 2020 due to the cancellation of the minor league season because of the COVID-19 pandemic.[7] Ferguson was released by the Dodgers organization on July 1.[8]
On June 17, 2021, Ferguson's contract was purchased by the Atlanta Braves organization.[10] He spent the remainder of the season split between the High–A Rome Braves and Double–A Mississippi Braves. In 22 appearances between the two affiliates, Ferguson compiled a 6–4 record and 2.23 ERA with 33 strikeouts across 32+1⁄3 innings.[11]
In 2022, Ferguson made 52 appearances split between Mississippi and the Triple–A Gwinnett Stripers, posting a combined 4.80 ERA with 64 strikeouts in 50+2⁄3 innings of work. He elected free agency following the season on November 10, 2022.[12]
Arizona Diamondbacks
On December 9, 2022, Ferguson signed a minor league contract with the Arizona Diamondbacks organization.[13] He spent the year with the Triple–A Reno Aces, pitching in 51 games and logging a 5.49 ERA with 86 strikeouts across 78+2⁄3 innings. Ferguson elected free agency following the season on November 6, 2023.[14]
Oakland Athletics
On November 15, 2023, Ferguson signed a minor league contract with the Oakland Athletics. In 14 games for the Triple–A Las Vegas Aviators, he recorded a 2.40 ERA with 24 strikeouts and 4 saves across 15 innings pitched.[15]
On May 7, 2024, Ferguson was selected to the 40-man roster and promoted to the major leagues for the first time.[16] On July 25, Ferguson earned his first career save, striking out two batters in a scoreless ninth inning against the Los Angeles Angels.[17]