"It is so surreal," the 22-year-old Kreider said. "It's not something that can really be explained. It is something that just has to be felt, but it was awesome. I'm just excited to give these guys an opportunity to play another game.
"There is no quit in this room."
New York, which erased 2-0 and 3-2 deficits, still trails the Eastern Conference semifinal series 3-1.
The Rangers will need to win again on Saturday in Boston to force a Game 6 back in Madison Square Garden.
The Rangers, outshot 40-32, won a faceoff deep in their zone, and Nash rushed the puck up ice. He stopped above the right circle and fed a hard pass in front that Kreider skated into and tipped past goalie Tuukka Rask for his first of the playoffs.
New York, 0-3 in overtime in these playoffs, was eliminated from the conference finals last year by New Jersey in extra time in Game 6.
"It is time for us to win an overtime game," Rangers goalie Henrik Lundqvist said. "This was a big one. It was such a great feeling to see that puck go in."
Kreider, who made his NHL debut in last year's playoffs, has six career postseason goals in just 25 games.
"I was lucky enough to play with Rick," Kreider said. "Just trying to go hard to the net. He's such a talented player. He was able to find my tape, and I tried to put it on net."
Derek Stepan and Brian Boyle scored tying goals in the third period for the Rangers, who even found success on the power play. Carl Hagelin netted New York's first goal of the game in the second period.
Lundqvist made 37 saves for New York, which managed only five goals total in the first three games against Boston.
Only three teams have lost a series after leading 3-0, but the Bruins are the most recent to do it in 2010 against Philadelphia.
"It's a resilient group," Kreider said. "The tone of the dressing room was the same as positive and upbeat. We're excited to play more hockey."
One more win will put Boston back into the conference finals for the second time in three years. The Bruins gave up a 3-1 lead to Toronto in the first round before rallying in Game 7 to advance.
"There is no panic here," Bruins coach Claude Julien said. "We have to go back home and play a better game."
Stepan got New York even at 2 just 1:15 into the third after a dump-in. Rask went behind the net to slow the puck down for defenseman Zdeno Chara, but Stepan forced a turnover when he surprised Chara from behind.
Stepan gathered the puck, came around in front and tucked the puck inside the left post for his team-leading fourth of the playoffs.
"We made some mistakes tonight, mistakes we haven't been making, mistakes you can't have, and they capitalized on them," Chara said. "They made us pay.
"These nights are going to happen. They played to win, and we didn't match their intensity at times."
The Bruins made the most of another power play and took a 3-2 lead just 2 seconds after a goalie interference penalty against Ryan McDonagh expired. Seguin got to his own rebound in close and shoved a shot past Lundqvist at 8:06.
However, the Rangers still wouldn't go away and they finally connected on the power play for the first time in the series and the third time in 41 man-advantages this postseason.
Boyle took a pass from Stepan in the slot and snapped a drive that nestled into the middle of the net at 10:00 after the Bruins were caught with too many men on the ice.
New York coach John Tortorella made desperate moves with his lineup, hoping to find some chemistry to spark his club. Tortorella benched star center Brad Richards, who had just one goal in the playoffs, and rugged forward Arron Asham in favor of seldom-used Kris Newbury and Micheal Haley.
"By no means is this a situation where I take him out and I'm blaming him," Tortorella said of Richards. "I need to make decisions about what I feel is right for our team to win tonight's game, and that's why I made that decision."
The Bruins used their power play to grab control in the second period, connecting twice in a span of 3:02 to take a 2-0 lead.
After Newbury was sent off for goalie interference, when he knocked down Rask, Horton got the scoring going. He tried to feed a pass from the bottom of the left circle into the slot, but the puck hit Rangers defenseman Michael Del Zotto and bounced back to Horton.
This time, Horton let a shot go that struck the inside of Lundqvist's left leg and caromed in at 4:39.
Lundqvist blocked a hard shot by Chara, who rattled a drive off of the goalie's mask. At the next stoppage, there was a brief delay as Lundqvist had repairs made.
Del Zotto took an interference penalty 1:25 after Boston took the lead, and Krug made the Rangers pay again. Krug, a rookie defenseman who made his NHL postseason debut in the series opener, fired a slap shot from the Stanley Cup logo in the Rangers' zone that sailed past Lundqvist and into the top right corner at 7:41.
Krug has scored in three of the four games he has played in this series, and his goal gave Boston as many power-play tallies at Madison Square Garden in this playoff year as the host Rangers had mustered to that point.
However, New York got a big break just 54 seconds later to cut the deficit in half.
As the Rangers were moving the puck up ice, Rask stumbled in the crease and fell at around the same time that Hagelin was backhanding a shot on net. Sliding as slowly as possible, the puck eluded Rask as he tried to recover in time to stop it.
"We need to be more focused, I need to be more focused," Rask said. "I just took a step to the side in what I think probably was a skate mark or something. I lost my balance and the rest is history.
"We gave them a couple of gifts, and it cost us the game."
It took nearly seven minutes before New York recorded its first shot on Rask -- a drive by defenseman John Moore -- and Boston controlled the period with a 12-4 edge in shots.
The Rangers are 5-6 in Game 4 when trailing 3-0. ... Before Game 1, the Rangers and Bruins hadn't gone to overtime against each other in the playoffs since March 27, 1958. ... Kreider, who made his regular-season debut against Boston on Jan. 19, had two goals in 23 games this season.