He pitched in 2014 for the Advanced Rookie League Pulaski Mariners, going 5–5 with a 4.52 ERA in 13 starts.[4] Littell pitched in 2015 for the Single-A Clinton LumberKings, compiling a 3–6 record and 3.91 ERA in 21 starts.[4]
He started 2016 with Clinton, and was promoted to the Bakersfield Blaze in July.[5][6] In 28 total games (27 starts) between the two clubs, Littell collected a 13–6 record, 2.66 ERA, and 1.16 WHIP.[4]
On July 30, 2017, the Yankees traded Littell and pitcher Dietrich Enns to the Minnesota Twins in exchange for pitcher Jaime García and cash considerations.[8] The Twins then assigned him to the Chattanooga Lookouts where he finished the season. In 27 total games (25 starts) between Tampa, Trenton, and Chattanooga, he went 19–1 with a 2.12 ERA and 1.12 WHIP.[9] The Twins added him to their 40-man roster after the season.[10]
Littell made his MLB debut on June 5, 2018.[11] In eight games in the majors in 2018, Littell went 0–2 with a 6.20 ERA, 25 hits, 14 strikeouts, and 11 walks in 20.1 innings. In the minors, he was 6–9 with a 3.98 ERA and a 1.357 WHIP.[4]
Littell moved to the bullpen full time in 2019. He went 6–0 in 29 games with a 2.68 ERA, 32 K, and 9 BB in 37 innings, while in the minors in 63 innings, he was 3–3 with a 3.71 ERA and 25 walks. He had a hard-hit rate of 52.5%.[12]
In 2020 in 6.1 innings he gave up five home runs among 12 hits. He had a 9.95 ERA with a 2.368 WHIP.[13]
On September 17, 2020, Littell was outrighted off the 40-man roster.[14] He became a free agent on November 2, 2020.
San Francisco Giants (2021–22)
On February 3, 2021, Littell signed a minor league contract with the San Francisco Giants, and received an invitation to spring training.[15][16] The Giants promoted him to the major leagues on April 30.[17] In the 2021 regular season, Littell was 4–0 with a 2.92 ERA in 63 games (2 starts) covering 62+2⁄3 innings in which he struck out 63 batters with the Giants; with Triple-A Sacramento, he had a 9.00 ERA.[18] His hard-hit percentage of 46.0% was in the bottom (worst) 5% of major league pitchers.[19]
On September 13, 2022, Giants manager Gabe Kapler came to the pitcher's mound to remove Littell from a game, after Littell had given up two earned runs on three hits and a walk on only 15 pitches.[20] Littell slammed the ball into Kapler's hand and angrily told Kapler he wanted to remain in the game.[21] The next day, the Giants demoted him to the Triple-A Sacramento River Cats.[22][23]
In 2022, Littell was 3–3 with a 5.08 ERA and a 1.376 WHIP with the Giants.[24] He was 0-1 with a 6.75 ERA with Triple-A Sacramento. The Giants waived him off the 40-man roster on November 9, 2022. When no team chose to pick him up, the Giants outrighted him to Sacramento.[25] He elected free agency on November 10.[26]
Texas Rangers (2023)
On January 12, 2023, Littell signed a minor league contract with the Texas Rangers organization.[27] He began the year with the Triple-A Round Rock Express, for whom he made eight appearances and recorded a 2.25 ERA with 16 strikeouts in 12.0 innings pitched. The Rangers never called him up from the minor leagues.[28]
Boston Red Sox (2023)
On May 5, 2023, Littell was traded to the Boston Red Sox in exchange for cash considerations.[29] He was selected to Boston's active roster the next day.[30] In two relief appearances for Boston, he surrendered three hits, three walks, and three runs in three innings pitched, for a 9.00 ERA. Littell was designated for assignment on May 10, five days after being acquired.[31]
Tampa Bay Rays (2023–present)
On May 12, 2023, Littell was claimed off waivers by the Tampa Bay Rays.[32] He pitched for both the Triple–A Durham Bulls (with whom he was 0-1 with an 18.00 ERA) and the Rays, which converted him into a starting pitcher. On August 4, he threw a career high 6 innings, allowing no runs and earning a win against the Detroit Tigers.[33] He ended the season 3-6, with a 4.10 ERA between the two major league teams.