[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.

[9] The Yankees traded Nelson and Donny Sands to the Philadelphia Phillies in exchange 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.

[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.

[17] He allowed one run in two innings of relief against the Miami Marlins in his only appearance, and was designated for assignment by the Phillies on September 7.