Kelly began his career as an apprentice with Arthur Cox's Newcastle United in 1982, becoming boot boy to former England captain and European Footballer of the Year Kevin Keegan.
He was loaned out to West Ham United in 1994, reaching the quarter-final of the FA Cup before losing 3–2 to Luton Town in a replay and being an unused sub in 16 Premiership games.
Kelly joined Neil Warnock's Sheffield United in 2003 reaching the semi-finals of the FA Cup before losing 1–0 to Arsenal at Old Trafford.
[5] He also reached the 2003 Football League First Division play-off final eventually losing to 3–0 to Wolverhampton Wanderers at the Millennium Stadium, Cardiff.
[6] Kelly played for the Ireland U19 national team that qualified for the 1983 UEFA European Under-18 Football Championships where despite remaining unbeaten in a group that included eventual winners, France, they were eliminated.
Ireland won their group stage before losing the semifinal 2–1 against hosts Russia in front of a 40,000 crowd in Dynamo Stadium, Moscow.
Ireland's exploits earned them a qualification for the 1985 FIFA World Youth Championships in Russia and a first UEFA medal but Kelly was refused permission to be released by his club Newcastle United.
Kelly made his Ireland U-21 debut in a friendly in 1985 against England at Fratton Park and played in the 1988 UEFA European Under-21 Football Championship qualifiers.
He was on standby for the 1990 and 1994 FIFA World Cup Finals as Jack Charlton went with an extra outfield player instead of the regulation three goalkeepers in his 22-man squad.