Callahan, a 6-foot-1, 216-pound rookie, was originally signed by Green Bay as an undrafted rookie out of Wesley College on May 6. After being released by the Packers on Oct. 13, he was claimed off waivers by the New Orleans Saints. Callahan was released by the Saints on Oct. 22 and claimed by the Cleveland Browns on Oct. 24, but was released on Nov. 29. He was signed to Green Bay’s practice squad on Dec. 2. In 2015, he became the first NCAA Division III quarterback to throw for 5,000 yards in a season, earning the Gagliardi Trophy, the highest award in Division III football.