He played representative rugby league for Great Britain at every age level from under 16's, 19's and 21's. He was also selected for England, Wales and Great Britain on the tour to Papua New Guinea, Fiji and New Zealand in 1996.
Critchley joined Keighley Cougars in 1995. In August 1996, he scored six tries for Keighley Cougars in a match against Widnes Vikings, breaking a club record which had stood for 90 years for most tries in a single match.[7]
In May 1997, Critchley was signed by Castleford Tigers in exchange for Adrian Flynn and an undisclosed transfer fee.[8] Castleford were bottom of the Super League, and hadn't won a single game when Critchley first arrived at the club, but he helped the club improve results during the rest of the season, and finished as the club's top try scorer.
In 1998, Critchley switched codes and joined rugby union side Newport. He returned to league during the rugby union off-season to play for Wakefield Trinity in 2000.[9]
Following the relaxation of eligibility rules, Critchley qualified to play for Wales. He was selected in the 40-man training squad for the 1995 Rugby League World Cup, but did not make the final squad.[10] He made his debut a year later, and went on to win eight caps for Wales between 1996 and 2001.[1] He was selected by Wales for the 2000 Rugby League World Cup,[11] making five appearances during the tournament, and scoring a try in Wales' 22–8 win in the quarter final against Papua New Guinea.[12]