Contreras split the 2018 season between the Low–A Staten Island Yankees and the Single–A Charleston RiverDogs, going a combined 0–2 with a 2.42 ERA and 60 strikeouts over 63+1⁄3 innings.

[4] On January 24, 2021, New York traded Contreras, Miguel Yajure, Maikol Escotto, and Canaan Smith-Njigba to the Pittsburgh Pirates in exchange for Jameson Taillon.

[7] He split the 2021 minor league season between the Double–A Altoona Curve and the Triple–A Indianapolis Indians, going a combined 3–2 with a 2.64 ERA and 82 strikeouts over 58 innings.

[8] On September 29, 2021, Contreras had his contract selected to the active roster, to make his MLB debut that night versus the Chicago Cubs.

[9] Contreras started the 2022 season in Triple-A Indianapolis, but on April 8, 2022, the Pirates recalled him from the minor leagues.

[12] In 2023, Contreras made 19 appearances (11 starts) for Pittsburgh, but struggled to a 3–7 record and 6.59 ERA with 55 strikeouts across 68+1⁄3 innings pitched.