Allen attended Florida International University (FIU) and played college baseball for the FIU Panthers as both a pitcher and a first baseman. In 2018, he was named a Freshman All-American by the NCBWA, Collegiate Baseball Newspaper, and Perfect Game and second team All-Conference USA as a utility player after posting a 5–5 record with a 3.89 earned run average and 85 strikeouts in 74 innings pitched while also batting .309 with two home runs and 16 runs batted in.[4] As a sophomore, Allen was named first team All-Conference USA after went 4–6 with a 3.11 earned run average with 120 strikeouts in 84 innings pitched and hit .276 with three home runs.[5] After the 2019 season, he played collegiate summer baseball with the Harwich Mariners of the Cape Cod Baseball League.[6] As a junior in 2020, Allen went 2–1 with a 2.45 earned run average in four starts batted .286 with one home run and two runs batted in before the season was cut short due to the coronavirus pandemic.[7]
Professional career
The Cleveland Indians selected Allen in the second round of the 2020 Major League Baseball draft.[8] Allen was assigned to the High-ALake County Captains at the beginning of the 2021 season, where he went 5–0 with a 1.58 earned run average in nine starts before being promoted to the Double-AAkron RubberDucks.[9][10] He had a 2.85 ERA with 76 strikeouts in 60 innings pitched after his promotion.[11] Allen returned to Akron at the beginning of the 2022 season before being promoted to the Triple-AColumbus Clippers after going 5–3 with a 3.33 ERA and 104 strikeouts in 73 innings over 13 starts.[12][13]
On April 23, 2023, Allen was selected to the Guardians' 40-man roster and promoted to the major leagues for the first time.[14] He made his major league debut the same day. Allen struck out 8, walked 1, and gave up 1 run, picking up the win in his first career MLB start. Allen was optioned back to the Clippers on June 29th, 2023 as the corresponding move for the recall of reliever Michael Kelly.