In 2015, as a freshman at Cal State Fullerton, Seabold appeared in 22 games (making 11 starts), going 5–4 with a 3.26 ERA in 69 innings, striking out 76 while walking only 12.[4] As a sophomore in 2016, Seabold became the Titan's Friday night starter a month into the year, pitching to a 7–6 record with a 2.48 ERA in 16 games (13 starts), striking out 96 and walking only nine in 83 innings.[5] He was named to the All-Big West Conference second team.[6] After the season, he played in the Cape Cod Baseball League for the Yarmouth–Dennis Red Sox, helping them win the league championship.[7][8] In 2017, as a junior, Seabold started 18 games, going 11–5 with a 2.96 ERA, earning a spot on the All-Big West Conference first team.[9][10]
On August 21, 2020, Seabold was traded to the Boston Red Sox, along with Nick Pivetta, in exchange for Brandon Workman, Heath Hembree and cash.[23] On November 20, 2020, he was added to Boston's 40-man roster.[24] Seabold began the 2021 season on the injured list due to elbow soreness.[25] He returned to pitching in July and was assigned to the Triple-AWorcester Red Sox.[26] On September 11, Seabold was added to Boston's active roster to make his major league debut.[27] He started that night against the Chicago White Sox at Guaranteed Rate Field, allowing two runs on three hits in three innings,[28] and was optioned back to Worcester the next day.[29] In 11 starts with Worcester, Seabold compiled a 3.50 ERA and a 4–3 record while striking out 52 batters in 54 innings.[20] After the regular season, Seabold was selected to play in the Arizona Fall League.[30]
Seabold began the 2022 season in Triple-A with Worcester.[31] He was added to Boston's active roster for a start against the Toronto Blue Jays on June 27; after taking the loss, he was optioned back to Worcester.[32] He was recalled by Boston on July 3 for a start at Wrigley Field,[33] resulting in a no decision, and optioned back to Triple-A the next day.[34] He was recalled on July 8, when Michael Wacha was placed on the injured list.[35] The next day, Seabold himself was added to the injured list with a right forearm extensor strain.[36] Seabold was optioned back to Worcester in late July,[36] and recalled to Boston for a week in late September.[37] In five starts with Boston, Seabold went 0–4 with an 11.29 ERA while striking out 19 batters in 18+1⁄3 innings.[38]
On January 17, 2023, Seabold was traded to the Colorado Rockies in exchange for a player to be named later or cash.[40] After struggling to a 7.18 ERA in 20 games, Seabold was demoted to the bullpen on July 20.[41] On December 6, Seabold was released by the Rockies.
Samsung Lions
On December 22, 2023, Seabold signed a one-year, $900,000 contract with the Samsung Lions of the KBO League.[42]
Personal life
Seabold has two younger brothers, Cade and Carson; their mother died in August 2015 at age 45 following a battle with cancer.[43]