in august 2001, guppy re-joined o'neill at celtic for £700,000, where he spent two-and-a-half years. during his time at celtic, they won the scottish premier league. after being released by celtic in january 2004 he temporarily re-joined leicester city but left them in the summer of 2004, to try to get to the us to play. he then spent a brief spell at leeds united in august 2004, scoring once against nottingham forest, before gaining a short term deal at stoke city followed by a short spell back at wycombe, scoring once against swansea city. he moved to the united states but his short stint in major league soccer with washington-based d.c. united was ended prematurely due to injury, and he was released by the club after playing in just five league games in which he was featured in a starting line-up alongside freddy adu in midfield.