In his first full professional season in 2017, Braymer pitched for the Low-A Auburn Doubledays and the Single-A Hagerstown Suns. He and Klobosits were both among several minor league pitchers brought over to pitch to the major league Nationals hitters as they prepared for the 2017 National League Division Series.[4]
Braymer led all Nationals minor league pitchers with a 2.28 ERA in 2018, pitching for the Suns and High-A Potomac Nationals. Along with Wil Crowe, he was named the Nationals' co-Minor League Pitcher of the Year.[5] He was one of eight Nationals prospects invited to participate in the Arizona Fall League after the 2018 season, where he played for the Salt River Rafters.[6]
Before the 2019 season, MLB Pipeline ranked Braymer as Washington's 25th-best prospect.[7] In late June 2019, he was promoted to the highest minor league level for the first time, joining the starting rotation of the Triple-A Fresno Grizzlies.[8]
Braymer was added to the Nationals' 40–man roster following the 2019 season.[9] He made his major league debut on August 28, 2020, giving up one run in two innings in a win over the Boston Red SoxatFenway Park.[10] In his rookie season, Braymer logged a 1.23 ERA across 3 appearances.
Braymer was assigned to the Triple-A Rochester Red Wings to begin the 2021 season. After struggling to a 1-5 record and 6.75 ERA in 7 appearances, Braymer was designated for assignment on June 20, 2021, following the selection of Gerardo Parra.[11] He cleared waivers and was sent outright to Rochester on June 24.[12] Braymer made 25 appearances (21 starts) for Rochester in 2021, working to a 7-8 record and 5.78 ERA with 79 strikeouts in 99.2 innings of work. In 2022, Braymer made 11 appearances (1 start) for Rochester, but struggled to a 6.75 ERA with 19 strikeouts in 18.2 innings pitched. He was released by the Nationals organization on May 27, 2022.
On May 17, 2023, Braymer's contract was purchased by the Colorado Rockies organization.[14] In 16 appearances (15 starts) for the Triple–A Albuquerque Isotopes, he struggled to a 1–7 record and 9.75 ERA with 42 strikeouts in 60 innings of work. On October 3, Braymer was released by Colorado.[15]