After struggling through the first two quarters in what has been an underwhelming series for him, Williams took charge. During the team's 28-17 run in the third quarter, when the Sixers cut into Boston's commanding lead and made the comeback believable, Williams kicked in nine points.
Williams said his team came out in the second half ready to fight, unlike in the first 24 minutes.
"We just started chipping away. It's one of those things where it's kind of a blur. We go from 12, 10, we make a three, they make a shot. Then, you realize with eight minutes to go that it's a six-point game."
The run cut Boston's lead down to just four points before the final quarter. Then, the Sixers outscored the Celtics by 13 to even the series at two games each.
In that third quarter, Williams hit three of his four shots from the field (including 1 of 2 from beyond the arc). He also energized the rest of the Sixers, pushing the ball after halftime and racking up four assists.
Williams subbed in for Jrue Holiday with 9:09 left in the quarter. After missing his first shot, he heated up around the four-minute mark, first hitting a three-pointer on a kick-out from Andre Iguodala.
Williams then connected on a series of runners, scoring five points in the last three minutes of the quarter.
Williams also came through to complete the comeback in the fourth. He scored four more points and contributed four assists. He helped seal it with his ability to penetrate.
With the Sixers clinging to a two-point lead, Williams cut inside and drew the Boston defense. He then kicked out to Iguodala, who nailed a 24-foot trey to provide the dagger, cementing the comeback.
"I don't think this really came down to one guy doing something," Williams said. "We all wanted that type of pressure."
Entering Friday's game, Williams had struggled against Boston, shooting just 32 percent from the field. He was also averaging 10 points per game - but he scored nine points in his nine minutes in the third Friday night.
The Sixers needed Williams to attack. Before Friday's game, coach Doug Collins said the team was at its best when charging toward the hoop rather than relying on jump shots. In Game 3, the Sixers shot 40.7 percent from the field as Boston ran away with the game.
The Sixers could have folded in the second half Friday, facing the double-digit deficit, Williams said. They could have stood around, hoping their jumpers started falling while the clock dwindled down. But they didn't.
"We started playing faster, started playing smarter," Williams said. "We played with speed. We realize they can have some struggles with that at times. We were able to have some success."