Harkin is in his third season with the Ducks and eighth in professional baseball. During the 2022 campaign with Long Island, the right-hander tallied a record of 10-8 with a 4.86 ERA in 24 starts, striking out a total of 88 batters in 127.2 innings pitched. He won each of his first five starts with the Ducks in 2021 before having his contract purchased by Toros de Tijuana (Mexico) on July 22. Harkin was originally selected by the Milwaukee Brewers as an amateur free agent in 2013 out of Sonoma State University in Rohnert Park, California.  

Harkin was the winning pitcher for Long Island in game two of the 2021 North Division Championship Series versus the Southern Maryland Blue Crabs at Regency Furniture Stadium on October 12th, firing seven scoreless innings on just four hits allowed while not issuing a walk and striking out six. In two playoff starts that season, he went 1-0 with a 2.08 ERA and just eight hits surrendered along with 12 strikeouts in 13 innings, a 0.85 WHIP and a .170 batting average against.