The Edmonton Oilers weren’t very good against Boston on Thursday night, and a big part of the problem was an inability to hold their own blue line.

Let’s start with the Boston Bruins exiting their own end of the rink. The Oilers have two players trapped deep while the Bruins have three forwards coming out of their own end, making this a three-on-three scenario.

Eberle (14) does kind of a weird thing here, cutting over to the wing through Patrice Bergeron (37) rather than staying at the centre of the ice; this opens up the right side for the Bruins and unsurprisingly they opt to pass in that direction.

Still, the Oilers are in good shape here. This is essentially a two-on-two rush with Eberle the fifth man; Schultz is playing Bergeron close on one wing so he isn’t a realistic pass option and that leaves Nikitin with the job of handling Reilly Smith (18) one-on-one. He’s already at the blue line while Smith has just crossed centre, so his job is simply to try and force Smith into making a play at the blue line – with Bergeron covered and Eberle trailing the play this shouldn’t be a problem.

Inexplicably, Nikitin doesn’t force the issue at the defensive zone blue line; instead he backs all the way in, playing Bergeron and Smith like this is a two-on-one situation despite the fact that Schultz is in really good shape to cover Bergeron (who realizing what’s up is booking it to the middle of the ice to give Smith an option). Eberle isn’t in a great spot after his weird decision to cut to the wing, but that’s decidedly an auxiliary issue; the real problem here is that Nikitin has rolled out the red carpet for Smith to enter the zone.

Schultz has his guy, Eberle has his guy, and Nikitin finally decides to stop backpedaling. The trouble is that he’s at the top of the circle by the time he decides to try and force the issue.

Smith, finally forced to make a play, realizes he’s in a good spot so he lets the shot go. Nikitin tries to block it, but instead gets used as a screen. Eberle still has his man, Schultz still has his man, but Nikitin’s decision to back all the way up to the hashmarks before making a play on Smith means that Boston is now guaranteed a shot attempt from a dangerous area.

Smith makes his shot, and it’s a tie game.

I’m picking on Nikitin here, partially because he was wretched against Boston but mostly because this particular play resulted in a goal against. He wasn’t the only guy to do this; Oscar Klefbom in particular was really bad at it, too. A few minutes before Smith scored, he hammered a puck off the goalpost off this zone entry:

It’s hard to tell from that angle, but this is a three-on-four rush by the Bruins. Brad Marchand has to beat both Teddy Purcell and Klefbom at the blue line just to gain the zone. But even with Purcell there to funnel Marchand right into Klefbom, Klefbom backs all the way up, giving Marchand all kinds of space to gain the zone with possession:

Marchand gains the zone, makes a short pass and Smith hits the post.

This is the kind of mistake that’s really interesting because a) defencemen face this situation all the time and b) it’s the kind of thing that can have a large impact on possession numbers. We know that there’s a massive difference in the number of shots a team gets when it is able to carry the puck into the offensive zone as opposed to being forced to dump and chase, and the defencemen who make these decisions correctly time and again are going to be forced to spend a lot less time defending their own zone against opponents who have the puck.

This is the one area where Martin Marincin really shines. Marincin has some notable weak points to his game, but one of his great strengths is that his gap is generally good when defending an opposition rush and he’s excellent at using his reach to prevent the other team from gaining the zone with possession.

It’s the kind of subtle thing that doesn’t stand out the way physical play in front of the net or a good outlet pass do, but it matters a lot all the same.