Justin Williams couldn't stop smiling after the final horn sounded on the Kings' come-from-behind 4-3 victory over the St. Louis Blues in Game 4 of their increasingly compelling first-round playoff series on Monday night at Staples Center.

It might have had something to do with the crisp white "Hockey Night in Canada" towel he had draped around his neck for being the Canadian Broadcasting Corporation's postgame guest, a coveted souvenir among players. But it had everything to do with his go-ahead goal 8:30 into the third period.

"That's the playoffs, that's battling all the way to the final buzzer, whether it takes 60 minutes, whether it takes 80 minutes or however long it takes," Williams said. "We needed a big third period. We needed a response. They had a couple of leads in the game and we were able to fight them off.

"Now is not the time to let off the accelerator. Now is the time to keep pushing."

Williams' goal rallied the Kings to a 2-2 tie in the best-of-7 series. Game 5 is Wednesday in St. Louis. Game 6 will be Friday at Staples Center.

Kings center Anze Kopitar scored his first goal since March 25 to tie the score at 3-3. He slipped behind the Blues' defense, accepted a pass from Dustin Brown and slammed the puck into the back of the net at 7:14 of the third period.

Then, with the crowd still buzzing about Kopitar's tying goal, Williams put the Kings ahead for good 4-3 by deflecting a perimeter shot by Mike Richards 1:16 later. The goal was reviewed by video replay in Toronto to see if Williams illegally struck the puck while his stick was above his shoulder.