The loss means Thunder have to win away to bottom-of-the-table Newham Neptunes on Saturday to seal a play-off place. Worthing will still finish in the top eight if they lose and Leicester fail to win at Derby.
Milton Chavis led Worthing with 32 points, 10 rebounds and five assists in a superb all-round display, while Hank Rivers chipped in with 23 points and 12 rebounds and Tomas Seduikis added 16 points for the hosts.