Thomas signed for Arsenal in 1982, turning professional on December 31, 1984, and he made his debut in the League Cup Semi-Final against North London rivals Tottenham. He was known for his athleticism, passing ability and his well-timed forward runs. The highlight of Thomas's Arsenal career came in the 1988-89 title decider, on 26 May 1989. Arsenal headed to Anfield needing to beat champions Liverpool by two clear goals to end an 18-year wait for the title. Thomas struck in the dying seconds of stoppage time to win it for the Gunners. Thomas was just 21 when he enjoyed his Anfield moment and went on to play 208 games scoring 30 goals. Thomas then went on to play for Liverpool for a fee of £1.5 million.