Hessenthaler, son of former Gills player and Manager Andy, forced his way in to first-team consideration following the arrival of Peter Taylor in October 2013.
He soon became a first-team regular, scoring an incredible first goal for the club from just inside the half-way line in a 4-2 victory against Coventry City at Priestfield in March 2014.
Having begun his youth career at Chelsea, Hessenthaler was released by the London club and joined Gills as a teenager, progressing through the system with the likes of Bradley Dack
and Callum Davies
He made his Football League debut against Rotherham United in November 2013, and signed a four-and-a-half year contract at the club three months later. Hessenthaler's aforementioned goal against the Sky Blues earned him the coveted Goal of the Season prize at the 2013/14 Player of the Year awards; on the same night he was voted the club's young player of the Year.