Estes made his professional debut with the Rookie-level Gulf Coast League Braves with whom he gave up nine earned runs over ten innings. He did not play a game in 2020 after the minor league season was cancelled due to the COVID-19 pandemic.[5] Estes spent the 2021 season with the Augusta GreenJackets of the Low-A East, starting twenty games and pitching to a 3–6 record, a 2.91 ERA, and 127 strikeouts over 99 innings.[6] His .181 batting average against was ninth in the minor leagues.[7] He was named the league's Pitcher of the Week twice during the season, and was named the league's Pitcher of the Year following the season's end.[8]
On March 14, 2022, the Braves traded Estes, Shea Langeliers, Ryan Cusick, and Cristian Pache to the Oakland Athletics in exchange for Matt Olson.[9][10] He was assigned to the Lansing Lugnuts of the High-A Midwest League for the 2022 season.[11] Over twenty starts, he went 3-7 with a 4.55 ERA and 92 strikeouts over 91 innings.[12] To open the 2023 season, he was assigned to the Midland RockHounds of the Double-A Texas League.[13] In early August, he was promoted to the Las Vegas Aviators of the Triple-A Pacific Coast League.[14] In 27 games (23 starts) between the two affiliates, Estes posted a cumulative 9–6 record and 3.74 ERA with 131 strikeouts in 137 innings of work.[15]
On September 20, 2023, Estes was selected to the 40-man roster and promoted to the major leagues for the first time.[16] In two starts for Oakland, he surrendered nine runs (eight earned), 12 hits with seven strikeouts over 10 innings pitched. Estes was optioned to Triple–A Las Vegas to begin the 2024 season.[17]
Estes spent a majority of the 2024 season in the Athletics starting rotation. On July 3, 2024, he threw a complete-game shutout against the Los Angeles Angels, striking out four batters and issuing one walk in the 5–0 victory.[18] Across 25 games (24 starts) with the Athletics, Estes went 7-9 with a 5.01 ERA and 92 strikeouts. He made six starts in the minor leagues with Las Vegas, going 2-3 with a 6.04 ERA.[19]
Estes was named the final starter in the Athletics starting rotation to begin the 2025 season.[20] Estes gave up six runs in each of his first two starts and was subsequently optioned to Las Vegas.[21] On August 17, 2025, while playing for Triple-A Las Vegas, Estes threw a fastball at the shoulder of Victor Robles of the Tacoma Rainiers. Robles, on a rehab assignment, had been hit by four Aviators pitchers that week, including Estes on August 12. Estes also hit Robles while playing for Oakland on September 5, 2024. Robles reacted to this repeated behavior by throwing his bat at Estes.[22][23] At the time, he had hit a total of 28 batters in nearly 100 appearances in the minors.[24] Estes was recalled by the Athletics on August 22 and made one appearance.[25] With the Athletics, Estes made three appearances (two starts) and went 0-2 with a 9.82 ERA over 11 innings. He made 15 starts for Triple-A Las Vegas and pitched to a 5.51 ERA over 80 innings. On September 18, Estes underwent surgery to address a herniated disc in his lower back, ending his season.[26]
Estes was optioned to Las Vegas to open the 2026 season.[27]
