The defending champions Thames Valley Tigers can do little more than win two games on successive nights, but Friday's 102-78 win over Birmingham Bullets and Saturday's 109-95 victory at Hemel Royals still failed to cut into Sheffield's lead.
The crucial result, also on Friday, was Sheffield's 89-77 win at second-placed Doncaster Panthers, when 11 successive points in the fourth quarter opened an 80-65 lead.
Tigers still have to play the Sharks three times in the League, but have six defeats compared to Sheffield's single loss. "We need help from somewhere," the Tigers coach, Mike Bett, said.
Doncaster could not supply it, despite playing in front of a 1,500 home crowd who saw Sheffield's American, Chris Finch, hit five three-pointers. The biggest three-point haul of the weekend came from Sunderland's Russ Saunders, who scored seven in the 101-91 victory over Chester Jets as the Scorpions won their first home league game of the season.