New York Yankees

Nelson attended Rutherford High School in Panama City, Florida. He drafted by the San Francisco Giants in the 31st round of the 2014 MLB draft, but did not sign and played college baseball at Gulf Coast Community College. He was then drafted by the New York Yankees in the fourth round of the 2016 MLB draft and signed.^[1]

Nelson made his professional debut with the Pulaski Yankees, going 0–3 with a 3.38 ERA over 21+1⁄3 innings. He pitched 2017 with the Charleston RiverDogs, compiling a 3–12 record with a 4.56 ERA over 22 starts, and 2018 with Charleston, Tampa Tarpons and Trenton Thunder,^[2][3][4] pitching to a combined 8–6 record with a 3.55 ERA over 26 games (25 starts) between the three teams. He pitched 2019 with Tampa, Trenton, and the Scranton/Wilkes-Barre RailRiders,^[5][6] going 8–3 with a 2.81 ERA over 18 games (17 starts), striking out 114 over 89+2⁄3 innings.

Nelson was added to the Yankees' MLB roster on July 26, 2020.^[7] He made his MLB debut in the August 1 game against the Boston Red Sox, pitching three shutout innings in relief, and was credited with the win.^[8] He finished his rookie campaign making 11 appearances and logging a 4.79 ERA with 18 strikeouts in 202⁄3 innings pitched.

In 2021, Nelson made 11 appearances for the Yankees, but struggled to an 8.79 ERA with 22 strikeouts in 141⁄3 innings of work. In a larger sample size with Triple-A Scranton, Nelson worked to a 3.81 ERA with 62 strikeouts in 29 games.^[9]

Philadelphia Phillies

The Yankees traded Nelson and Donny Sands to the Philadelphia Phillies for T. J. Rumfield and Joel Valdez on November 19, 2021.^[10] On September 9, 2022, he recorded his first career save, pitching in relief of Brad Hand in a 5–3 victory over the Washington Nationals.^[11] In 2022, Nelson worked mainly as a long reliever, making 47 appearances for the Phillies and registering a 4.85 ERA with 69 strikeouts in 682⁄3 innings of work.^[12]

Nelson made only one appearance for Philadelphia in 2023, recording the win after allowing one run with three strikeouts across 5+1⁄3 innings against the New York Mets.^[13] Nelson was optioned to the Triple–A Lehigh Valley IronPigs to begin the 2024 season.^[14]