The American Dorsey top-scored with 28 points as he and his Barbadian team-mate, Nigel Lloyd, survived most of the fourth quarter on four fouls, while the young England international, Chris Haslem, won the battle of the boards against Sheffield's John Amaechi.
Sheffield's own title chances collapsed with three successive defeats after winning the League Trophy final on 8 March, and they did not end the sequence until Saturday's 124-86 win at bottom club Watford Royals.
Last night they led Birmingham 84-81 with seven minutes to play, but were held scoreless for nearly four minutes as 6ft 11in Haslem rebounded impressively at both ends of the court. Birmingham's 11-0 run included five points from Dorsey and put them 92-84 ahead to stun the Sheffield Arena crowd in the curtain-raiser to last night's All Star game.
Geno Ford scored Leicester's last eight points in a 92-90 victory over Worthing Bears, a success that keeps the Riders in a three-way fight with Derby Storm and Chester Jets for the last place in the play-off quarter- finals line-up.
The Jets lost 100-83 in front of 4,000 Newcastle Eagle fans on Saturday, but Derby recorded their third successive victory by beating Manchester Giants 95-77 after ending the game with a 14-6 run.