Gillespie signed for Manchester United on leaving school in the summer of 1991, being a member of the FA Youth Cup winning side in 1992.
On 20 August 1995, the News of the World carried reports that Gillespie was subject of an approach from Alex Ferguson to return to Manchester United to fill the gap on the right wing being left by the sale of Andrei Kanchelskis to Everton, but the return to Old Trafford never happened and United instead turned to up-and-coming youngster David Beckham to occupy that position.
18 years later, Gillespie confirmed that Ferguson did contact him regarding a possible return to Manchester United, but claims that he heard nothing more about the prospective transfer after that original telephone conversation with his former manager.
[8] Gillespie stayed at Newcastle for three and a half years and during this time he played 143 games, including 15 European ties (in both the Champions League and UEFA Cup) and scored 13 goals.
In both the 1995–96 and 1996–97 seasons he helped Newcastle to finish second in the Premier League (runners up to Gillespie's former club, Manchester United, on both occasions), being a key member of "The Entertainers".
Initially injured from a Phil Neville tackle in a 0–2 defeat at Old Trafford on 27 December 1995 causing him to miss the following three games, at the end of the 1995–96 season Gary Lineker, then a BBC pundit, said that one of the main reasons that Newcastle lost out on the title race was because they dropped Gillespie (who had been supplying Newcastle's forwards with a stream of good crosses) for several key games in the latter part of the season.
He also scored what he later claimed was his best goal for the club when playing up front due to an injury crisis at home to Blackburn Rovers in 1-1 draw on 25 October 1997.
However, a foot injury sustained in a 0–2 defeat at Tottenham Hotspur on 25 April 1998 meant, despite a fitness test, he was not in the squad for the final and Newcastle lost to Arsenal.
He returned to the Blackburn side for the final months of the 2000–01 season, as the club gained promotion back to the Premier League.
He also started in the 2002 Football League Cup Final, setting up a goal by Matt Jansen in the 2–1 victory over Tottenham Hotspur.
In March 2004, Gillespie and teammates Frank Sinclair and Paul Dickov were held in a prison cell for a week in La Manga, Spain, while charges were made against six more Leicester players.
In his first season at the club, Gillespie played a role in Sheffield United's successful promotion campaign to the Premier League.
However, McCall insisted Gillespie was only training with the club to stay fit and help out the younger players, and not on trial.
[26] In August 2010, Gillespie's former international teammate Michael O'Neill invited him to play in a friendly for Shamrock Rovers in a reserve game against his first club, Manchester United.
Gillespie came out of retirement in 2020, aged 45, to play for newly-formed Mid-Ulster Football League side FC Mindwell, a team set up to raise awareness of mental health issues.
Gillespie was investigated by the Irish FA for his involvement in a fracas with George McCartney on the trip back home from a game in Iceland in September 2007.
[4] Reviewer Robbie Meredith of When Saturday Comes wrote that "It is too cliched to claim that Gillespie achieves redemption at the end of his tale.