He has previously played in MLB for the Minnesota Twins, San Francisco Giants, and Boston Red Sox.

Littell attended Eastern Alamance High School in Mebane, North Carolina.

[2] He signed with Seattle, forgoing his commitment to play college baseball at Appalachian State University.

[4] Littell pitched in 2015 for the Single-A Clinton LumberKings, compiling a 3–6 record and 3.91 ERA in 21 starts.

[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 November 18, 2016, the Mariners traded Littell to the New York Yankees in exchange for pitcher James Pazos.

[15] On February 3, 2021, Littell signed a minor league contract with the San Francisco Giants, and received an invitation to spring training.

[28] 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.

[31] In two relief appearances for Boston, he surrendered three hits, three walks, and three runs in three innings pitched, for a 9.00 ERA.

On August 4, he threw a career-high 6 innings, allowing no runs and earning a win against the Detroit Tigers.