Kelly progressed through the youth set-up at Sheffield United before making his first-team debut during a 3-1 away defeat to Coventry City in April 2016.
A loan spell to then-Avenue`s National League North rivals Stalybridge Celtic followed later that year and the young defender made ten appearances during his stay at Bower Fold.
At the end of the 2016/17 season, Kelly was released by newly-promoted Sheffield United and Port Vale snapped him up on an initial one-year contract.
Also capped by the Republic of Ireland's under-18 and under-19 sides at international level, the 20-year old has been allowed to move to the Horsfall Stadium by new Vale boss, former Gateshead manager Neil Aspin.