The next year, Jannis split the season between the Low-A Hudson Valley Renegades and the High-A Charlotte Stone Crabs, posting a cumulative 4–3 record and 3.30 ERA with 45 strikeouts in 57.1 innings of work.
On July 29, 2014, Jannis signed with the Southern Maryland Blue Crabs of the Atlantic League of Professional Baseball.
[4] Jannis made 10 appearances for the Blue Crabs in 2014, registering a neat 2.37 ERA and 4–1 record with 36 strikeouts in 57.0 innings pitched.
On March 17, 2015, Jannis signed with the Long Island Ducks of the Atlantic League of Professional Baseball.
In 2018, Jannis split the year between Binghamton and the Triple-A Las Vegas 51s, posting a cumulative 10–8 record and 4.19 ERA in 26 appearances.
[11] He allowed 7 runs in 3+1⁄3 innings of relief in his MLB debut in a 13–0 loss to the Houston Astros at Camden Yards the next night on June 23.
On July 30, 2022, Jannis signed with the High Point Rockers of the Atlantic League of Professional Baseball.
Jannis made 11 appearances for the Rockers to close out the year, registering a 2.72 ERA with 44 strikeouts in 39.2 innings pitched.
[21] On August 27, 2024, Jannis signed with the High Point Rockers of the Atlantic League of Professional Baseball.