Sampson played the 2013 season with the Bradenton Marauders, finishing 5-8 with a 5.14 ERA in 140 innings.[5] He started the 2014 season with the Altoona Curve.[6][7] In July he was selected to play in the Eastern League All-Star Game, but was forced to sit out the game by the Pirates.[8] In August he was promoted to the Triple-A Indianapolis Indians after posting a 2.55 ERA with Altoona. Overall, he went 11–6 with a 2.96 ERA and 109 strikeouts.
Sampson made his Major League debut on June 18, 2016 against the Boston Red Sox, relieving the injured Wade Miley.[10][11] Scheduled to replace Miley in the rotation, Sampson suffered a torn flexor tendon while warming up before his first major league start five days later against the Detroit Tigers, which required season-ending surgery later that month.[12][13][14][15]
Texas Rangers
On November 2, 2016, the Texas Rangers claimed Sampson off of waivers.[16][17] In 2017, Sampson rehabbed from the torn flexor tendon injury and made eight minor league appearances that season, going 2-2 with a 3.45 ERA in 31.1 innings with the AZL Rangers, Down East Wood Ducks, and the Round Rock Express.
Sampson spent the first 5 months of the 2018 season with the AAA Round Rock Express, going 8-4 with a 3.77 ERA in 126.2 innings.
Sampson was recalled to the Texas Rangers on September 4, and on September 11, 2018 Sampson made his first career MLB start. Sampson finished 2018 with a 0-3 record and a 4.30 ERA in 23 major league innings. Sampson was non-tendered by Texas after the 2018 season, and became a free agent on November 30, 2018.[18]
On December 27, 2018, Sampson re-signed with the Rangers on a minor league contract with an invite to major league spring training.[19] Sampson was assigned to the AAA Nashville Sounds on March 28, 2019.[20] On April 1, 2019, the Rangers purchased Sampson's contract and recalled him to the major league roster.[21] On June 8, he recorded his first career complete game versus the Oakland Athletics.[22]
Sampson finished the 2019 season going 6–8 with a 5.89 ERA over 125.1 innings.
He was 9-12 with a 5.40 ERA. He became a free agent following the season.
Chicago Cubs
On May 10, 2021, Sampson signed a minor league contract with the Chicago Cubs organization.[24] With the Triple-A Iowa Cubs, he was 4-5 with a 4.96 ERA. On August 18, his contract was selected by the Cubs.[25] Sampson pitched to a 2.80 ERA with 28 strikeouts in 10 appearances with Chicago. On November 5, Sampson was outrighted off of the 40-man roster.[26]
He returned to the organization, signing a minor league contract on March 19, 2022.[27] On May 10, he was designated for assignment,[28] and subsequently claimed via waivers by the Seattle Mariners three days later.[29] Though Sampson was assigned to the Tacoma Rainiers, he did not play for the team before being designated for assignment a second time on May 21.[30][31] He cleared waivers and was sent outright to Triple-A on May 24, but rejected the outright assignment a day later and elected free agency.[32] On May 31, 2022, Sampson re-signed with the Cubs on a minor league contract. On June 16, Sampson was selected back to the active roster.[33] He made 21 appearances (19 starts) for Chicago in 2022, pitching to a 4-5 record and 3.11 ERA with 73 strikeouts in 104.1 innings of work.
On November 18, 2022, Sampson signed a one-year, $1.9 million contract with the Cubs, avoiding arbitration.[34] In spring training in 2023, Sampson competed with Hayden Wesneski for the fifth starter role behind Marcus Stroman, Jameson Taillon, Drew Smyly, and Justin Steele. He was optioned to Triple-A Iowa on March 25, after manager David Ross announced Wesneski had won the job.[35] He made 2 starts for Iowa before undergoing a meniscal debridement surgery on his right knee on May 7.[36] He was placed on the 60-day injured list on May 15.[37] On July 24, Sampson was activated from the injured list. However, upon his activation, he was promptly removed from the 40–man roster and sent outright to Triple–A Iowa.[38]
Tampa Bay Rays
On August 1, 2023, the Cubs traded Sampson, Manuel Rodríguez, and international free agent bonus pool space to the Tampa Bay Rays in exchange for Josh Roberson.[39] Sampson did not appear for the organization and was released two days later.[40]
Texas Rangers (second stint)
On February 13, 2024, Sampson signed a minor league contract with the Rangers.[41]