The St. Louis Blues were confident they could push the Los Angeles Kings to the brink of elimination when they took a one-goal lead into the third period.

Then the defending Stanley Cup champions pushed back and this highly entertaining first-round series became all even again.

Anze Kopitar tied it with 12:46 to play, Justin Williams tipped home the go-ahead goal 76 seconds later, and the Kings evened their first-round series with a 4-3 victory over the Blues on Monday night.

Jeff Carter and Dustin Penner also scored for the Kings, who responded to a late deficit with the same tenacity that made them champs. Before the building had even quieted from the celebration of Kopitar's goal, Williams adroitly tipped a puck out of mid-air past Brian Elliott for the winner.

After four games of a remarkably even series, these two teams are level heading back to St. Louis for Game 5 on Wednesday night.

"That's playoffs," Williams said. "That's battling all the way to the final buzzer. We needed a big third period, and we responded. We're an experience team. We've been through a lot, and we knew we were facing a daunting task going back to St. Louis down 3-1, and we found it in ourselves. This is a group that's been in pressure situations before, and we know what we have to do to overcome it."

Mike Richards had two assists for Los Angeles, which dropped the first two games in St. Louis and barely survived for a 1-0 victory in Game 3. The Kings erased an early two-goal deficit and a third-period deficit in Game 4 to earn their ninth consecutive home victory since March 23, and Game 6 will be back at Staples Center on Friday.

"The resilience of our team is amazing," said Kopitar, who ended a personal 19-game goal drought. "To keep coming back and coming back like that, it's incredible. To be down 2-0, and then down 3-2 in the third period, it shows what we're capable of overcoming."

T.J. Oshie scored his first two playoff goals for the Blues, who had the champs on the brink of serious trouble before Kopitar and Williams beat Elliott, who stopped 25 shots.

"It's a tight series," said Blues captain David Backes, who scored 1:12 into the game. "We have to bring it every night. When our 20 guys are on the same page, we have a heck of a team. If we stray a little bit off of it, then it's a coin flip. Scoring three on them is fine and dandy, but giving up four goals is not our style."

The Kings hadn't won a playoff game after trailing by two goals since 2001, and they hadn't rallied from a third-period deficit to win a postseason game since the first round last year.

The Blues tried to protect a late lead in front of a raucous Los Angeles crowd, but they couldn't stop Kopitar, the Kings' perennial scoring leader. The Slovenian forward hadn't found the net since March 25, and acknowledged the struggle was weighing on him — but he gave Elliott no chance on his shot in front.

Moments later, Williams slipped in front of Elliott and expertly tipped home Richards' shot from the boards. A video review couldn't conclusively determine whether Williams' stick had been illegally high.

"You play all of last season and all of this season to build confidence in yourselves for situations like this," Richards said. "They've got a great team over there, and there's a lot of similarities between us. It's the smallest things that make the difference."

Jonathan Quick was tested in the final seconds after St. Louis pulled Elliott for an extra attacker, but he finished up his 19-save performance as the sellout Staples Center crowd waved white towels to celebrate another gritty postseason win.

"They took the game to another level tonight, and we didn't have an answer," Blues coach Ken Hitchcock said. "We made two mistakes, two really poor mistakes to give them odd-man rushes to get them back in the game, but even when it was 3-2, they were playing better than we were. ... We didn't manage the puck very well in the second and third period really at all, and paid for it dearly."

Both teams struggled offensively during the first three games, never leading by more than a goal. After the Blues' identical 2-1 victories at home, Quick posted his fifth career playoff shutout in Game 3.

But the Blues and Kings scored four goals in the first 14½ minutes of Game 4 and combined for seven goals — the same number they scored in the first three games of the defense-dominated series combined.

Staples Center fell silent after the Blues took the first multigoal lead of the series in the first 4:32, but the Kings swiftly answered.

Richards got the puck along the boards and got it to Carter, who led the Western Conference with 26 goals in the regular season, but had managed just nine shots and a minus-2 rating in the first three games.

The Kings evened it with a 3-on-1 finished by Penner. The two-time Stanley Cup winner got his first playoff goal since his overtime winner to end last season's Western Conference finals in Phoenix.

Oshie put the Blues back ahead shortly after a second-period timeout, sending a rebound of Vladimir Sobotka's shot over a prone Quick at a sharp angle.

NOTES: Blues F Vladimir Tarasenko made his NHL playoff debut, replacing Adam Cracknell on the fourth line. Cracknell hadn't been playing extensively for St. Louis, and Hitchcock wanted better offensive skill in the lineup after several missed scoring opportunities in Game 3. ... Los Angeles dressed seven defensemen for the second straight game, sitting forwards Jordan Nolan and Brad Richardson in favor of Alec Martinez, who picked up an assist in both games.