Dethridge was a right-handed batsman who bowled right-arm fast-medium. Dethridge made his debut for Bedfordshire in the 1982 Minor Counties Championship against Hertfordshire. Dethridge played Minor counties cricket for Bedfordshire till 1983, which included 11 Minor Counties Championship matches.
He made his only List A appearance against Somerset in the 1992 National Westminster Trophy.
In this match, he scored 31 runs before being run out. With the ball, he claimed a single wicket, that of Vic Marks, for the cost of 21 runs from 7 overs.
His performance in this match earnt him the man-of-the-match award.