Gerard came to prominence with Glenavon in the early nineties with his explosive change of pace and accurate finish which earned him a dream move from Mourneview Park to White Hart Lane in 1992.
McMahon had started with Glenavon as a 14 year old and had only broken into the Glenavon first team in the second half of the 1991/92 season, making his Irish League debut against Newry in February 1992, and established himself in the side for the rest of the season. It was his performance in the 4-0 Bass Irish Cup sixth round replay win against Glentoran that saw scouts from some of England’s biggest clubs inquiring about him, and by the middle of March a transfer had been agreed with Tottenham Hotspur. Glenavon comfortably cruised to the final of the Irish Cup and, in his last game before his £100,000 move to Spurs, McMahon scored the free-kick which defeated Linfield 2-1.
After his move to London it took him quite a while to settle, with the departure of Terry Venables, and the arrival of Ossie Ardiles. However, he persevered and was eventually rewarded when his long-awaited first-team chance came at the end of the 1994-95 season. McMahon’s Spurs debut came in May 1995, and he was a regular in the first-team squad throughout the following season, without really establishing himself in the starting eleven.
In May 1995 he won the first of his seventeen caps when he played for Northern Ireland against Canada in Edmonton.
McMahon found his first-team opportunities at White Hart Lane limited and so, in September 1996, he stepped down a division in order to further his career. The Stoke manager, Lou Macari paid £450,000 for his signature, and made McMahon a regular in the starting eleven, but with Brian Little replacing Macari in the summer of 1997 it seemed that McMahon didn’t belong in Stoke’s first-team plans either.
In February 1998 St Johnstone signed McMahon from Stoke for £85,000. Again however McMahon found himself out of the first-team following a change of manager, with Paul Sturrock leaving St Johnstone in 1999, and in the summer of 2000, when his contract expired, McMahon was allowed to leave.
After trials with Notts County and Macclesfield, McMahon returned to Glenavon in August 2000, initially on a short term contract, but after a month Colin Malone convinced him to sign a permanent deal. It proved a productive move as the Lurgan Blues finished as Irish League runners-up, thanks largely to an inspirational McMahon, who was arguably the leagues best player with his, pace, control, pinpoint passing and an eye for goal. McMahon was appointed club captain for the 2001/02 season, and nearly earned a surprise international recall when Sammy McIllroy came to watch him in the UEFA Cup tie against Scottish side Kilmarnock. In December 2002 in a home game against Glentoran, a horrible tackle led to both the bones in his leg being broken, leading to three operations and ruled him out of football for two seasons. In his absence, Glenavon really struggled, and despite his appointment as assistant-manager, they were relegated to the Irish League Intermediate Division One at the end of the 2003/04 season.
McMahon has since returned to fitness, helping Glenavon regain their Premier League position as play-off winners in 2005, and subsequently consolidate their top-flight position the following season. Remarkably, despite the injury, and the subsequent lack of pace, McMahon remains a bright light in the Glenavon side, and has since recovered froma another broken leg to maintain his status as the most gifted and creative player in a Glenavon shirt.