Sims made seven appearances as a freshman on the
Mississippi State Bulldogs baseball team in 2020 and compiled a 3.46 ERA before the season was cancelled due to the
COVID-19 pandemic.[4] In 2021, he became the team's
closer.[5][6][7] For the season, he made 25 relief appearances and went 5-0 with a 1.44 ERA, 100 strikeouts, 15 walks and 13 saves over 56+1⁄3 innings.[8] Sims, alongside
Will Bednar, threw a combined one-hitter against the
Vanderbilt Commodores in the final game of the
2021 College World Series, leading the Bulldogs to their first ever championship.[9] He was named to the
USA Baseball National Collegiate Team after the season.[10] Sims entered the 2022 season as a top prospect for the upcoming draft.[11] For the season, he moved into the
starting rotation.[12][13] He was named the team's Opening Day starter and pitched seven innings in which he gave up one earned run, seven hits, no walks, and 13 strikeouts in a 3-0 loss to
Long Beach State.[14][15] On March 4, in a game against the
Tulane Green Wave, Sims was removed in the fourth inning due to a right arm injury.[16] On March 14, it was announced that he had torn his
ulnar collateral ligament and would undergo
Tommy John surgery, forcing him to miss the remainder of the season.[17] Over 15+2⁄3 innings pitched in 2022, he compiled a 1.15 ERA and 27 strikeouts.[18]
Sims made his professional debut in 2023 during a rehab assignment with the
Arizona Complex League Diamondbacks, and was later assigned to the
Visalia Rawhide.[21] Over 24+1⁄3 innings pitched during the season, he went 0-4 with a 5.47 ERA and 28 strikeouts.[22] He was assigned to Visalia to open the 2024 season.[23]