The Raptors overcame the loss of superstar Vince Carter, who injured his right quadriceps with 4:42 left in the first quarter and did not return. He spent the second half on the bench with his leg bandaged.
The Raptors squandered a 10-point halftime lead but forced overtime on Jalen Rose's six-foot jumper with one second remaining.
After each team came up empty on three straight possessions late in overtime, Williams' jumper gave Toronto a 76-74 lead. Scoreless in the first half, Williams added a free throw with 4.8 seconds left to clinch the win.