For the first time all series, the Islanders out shot the Bruins (34-29) and generated more scoring chances (40-27). They also played a strong defensive game that included plenty of physical play and good goaltending from Semyon Varlamov.
The series now shifts from Nassau Coliseum back to TD Garden in Boston for a pivotal Game 5 on Monday night.
Here are three takeaways from Game 4.
1) Mathew Barzal's breakout performance
The Islanders' best forward struggled offensively for most of the playoffs and failed to score in each of his team's first eight games. Barzal has been much better in the last two matchups, though, and Game 4 was his best performance of the postseason so far.
Barzal battled B's forward Curtis Lazar along the boards for around 10 seconds in the second period, fighting him off and eventually drawing a penalty before feeding a pretty pass to Kyle Palmieri in front of the net. Palmieri shot the puck past B's goalie Tuukka Rask to even the score at one.
Barzal scored the game-winning goal in the third period when he batted a puck out of mid-air and into the B's net. It was Barzal's second tally in the last two games -- he also scored the tying goal in the third period that forced overtime in Game 3.
Barzal's resurgence is a huge reason why the series is tied, and his next challenge is making this kind of offensive impact in matchups played at TD Garden, where he struggled quite a bit in Games 1 and 2. The Bruins will have the last line change as the home team in Game 5, so you can bet Barzal will face plenty of the Bergeron line and/or the Charlie McAvoy-Matt Grzelcyk pairing Monday night.
2) Rare quiet game from B's top line
The Bruins' top line gave its worst performance of the series.
Bruins captain Patrice Bergeron had tallied at least one point in each of the first three games of this series (one goal, three assists overall), but he was held scoreless Saturday night, which saw his four-game playoff point streak end.
Bergeron tallied just two shots on net in 18:11 of ice time. He also was poor in the faceoff circle, losing 14 of his 24 draws. He went 6-of-18 on faceoffs in Game 3. Bergeron is one of the best faceoff men in the league, so his troubles in this area of late are not only surprising but also a bit concerning for Boston.
One or more of Brad Marchand, David Pastrnak and Bergeron had scored in every game of this Round 2 series before failing to find the back of the net in Game 4.
Pastrnak had a glorious opportunity to give the Bruins a 1-0 lead in the first period but missed a completely wide open net and hit the post.
In addition to not scoring, this line also failed to generate puck possession and scoring chances at its normally high rate.
The Bruins were even in shot attempts but minus-6 in shots on net and minus-2 in scoring chances during the 11:25 that the Bergeron line was on the ice during 5-on-5 action. The B's typically tilt the ice pretty heavily in their favor with the first line on the ice, but that wasn't the case in Game 4.
3) B's waste another good Tuukka Rask game
Tuukka Rask was one of the few Bruins players who actually played well in Game 4. He made 30 saves on 32 shots, including seven stops on high-danger scoring chances, per Natural Stat Trick.
The winning goal was batted out of mid-air by Barzal after a blocked shot. Rask admitted after the game he couldn't see the puck until it was in the net, which makes sense given the traffic in front. It was that kind of frustrating night for the Bruins, who wasted another excellent performance from their goalie.
Shots were 27-18 Islanders over the final two periods and the B's didn't tally a single shot over the final 6:18 of regulation. The only reason they were still in the game was Rask, whose save percentage in the series stands at .926 through four games. He actually increased his playoff save percentage from .934 to .935 after Game 4.
The veteran netminder has allowed two goals or fewer in three of the four games in Round 2. He's done his job so far.