By: Lydia Murray | Follow Me On Twitter @lydia_murray12
Earlier today, I published an article using an offensive shot heatmap from on the Bruins’ 2019-20 season to analyze their shot patterns and identify areas for them to work on in the playoffs. You can check that out here. Now, let’s take a look at how they were defensively in the 2019-20 season, and what areas they need to work on in the playoffs. Keep an eye out for another article coming later some heatmaps of power play and penalty kill. Also, be on the look for a deep dive one using skater good/bad/fun/dull graphs!
A Short Introduction to Shot Heatmaps
Before I begin, here’s a short overview of how to read these heatmaps for those of you who don’t know or need a refresher. This is the exact same intro I did on my first article, as is the “defining areas” of the ice section. So, if you’ve already read that one, you can probably skip right over this. But, if you didn’t, or just want another refresher, read on.
This is just a basic overview of how these heatmaps work. If you want to see a really in-depth analysis, you can check one out (albeit of the San Jose Sharks) here. But anyway, these maps illustrate the number of unblocked shots (not necessarily on goal) for or against a team compared to the league average, and where those shots are coming from. Blue means that fewer unblocked shots are generated from a given spot than the league average, whereas red means more are generated than the league average. The deeper the color, the further away from the league average a team is from that spot. White means that shots are being generated at the league average from that particular spot.
With this in mind, on offensive graphs, blue is good, and red is bad. Obviously, you want your team to be generating a ton of shots, and ideally, they’ll be producing more than most other teams. On the other hand, for defensive graphs, the opposite is true. When an area is blue, it means that team is letting less unblocked shots through than the league average. It goes without saying that’s a great thing. The fewer shots that get through unblocked, the fewer chances an opponent gets to score.
Defining Areas of the Ice
Before I get started with the actual heatmaps, there’s just a few more things I want to go over. Pictured above is an example of the heatmaps you’ll see in this article as it was directly on the website. This is great on its own, but I decided to add a few more things to aid in my analysis.
As you’ll see, I’ve added a box and a trapezoid to the above graph (as well as made the crease more obvious). My apologies for the subpar photo editing job, I don’t have access to the best software and I’m not too skilled at it either. But, it’s good enough for the purposes of this article. Please note, these outlines may be off a little bit, but if they are, it’s not by much as I was as exact as possible with the tools I had.
I’ve added these areas to aid in my analysis of these graphs. The box area I have outlined is known as the “slot”, and shots from this area are considered “high danger”. The trapezoid is known as just that, and shots from that area are considered “medium danger”. Shots from anywhere else on the ice are considered “low danger.” According to this article, in the high danger area, shots have at least a 10% chance of going in. The article also says that shots from the medium danger area have a 3-10% chance of going in, while low danger shots have at most a 3% chance of going in.
To be clear, those percentages are averages, as some shots obviously stand a better chance of going in than others, even from within those areas. For example, a shot from the backdoor of the net that’s wide open has a much better shot than one that’s coming from right out front with the goalie square to it. But anyway, with all of that out of the way now, let’s get into the actual analysis these things.
Now, Onto the Actual Analysis
Outstanding Defense in the Slot
The first thing that sticks out to me here is the same thing that stuck out to me on the offensive map, except this time, it’s good. The Bruins do an incredible job of suppressing or blocking shots throughout the entire slot. In most of the slot, the excess shots per hour rate is -0.5. That’s 5 fewer shots that get through per hour from those spots than the league average. That may not sound like a lot, but it’s actually incredible. Think about it, teams usually average 30-40 shots a game. So, to have, on average, five fewer shots than the league average getting through from one particular area of the ice, is outstanding.
The slot is the area the “high danger” shots come from. That means statistically, it’s the most dangerous area of the ice for goals off the initial shot. So, for the Bruins to be defending it that well is an excellent sign. Between that and how good their goalies are, it’s no surprise the Bruins let up as few goals as they do.
Excellent in the Left Circle Too
Another area the Bruins are excellent at defending according to this map is the left circle. There’s a red spot in the left of the circle, but it’s in the “low danger” scoring chance area and at a bad angle to the net, so it’s really not a concern. They can’t defend everywhere on the ice above league average, and if there’s a good spot to defend a little below the league average, that’s it.
Other than that spot, the Bruins do an excellent job of defending the left circle. They’re not as good there as they are in the slot, but it’s close. They also don’t have to be as good defending there, as it’s statistically a less dangerous area of the ice for initial shots. They let about two or three less unblocked shots get through from that spot in an average game, and that’s great. It means they don’t let a lot of one-timers through on the left side, as the circles are really popular places for them, which is good news. One-timers are the initial shots that beat goalies the most because they have way less time to react and then get their feet set before the puck is there. So, the less of them they let through, the better.
Left Point Good and Bad
The Bruins defend the lower right portion of the left point about as well as they defend most of the left circle. That’s great news because it means they’re getting in the primary lane to the net from the point. That means a lot less unblocked shots are getting through from the point than would otherwise, which means fewer chances for players to pounce on the big, juicy rebounds those shots often produce. That’s always a good thing.
That being said, the lower left side of the left point could use some work. But, I am far less concerned about this spot than the right point (more on that later). Most of the red area over there is at a weird angle to the net. While that could make it more likely to sneak past the goalie on the first shot than one that’s straight on, not a lot of goals are scored on initial point shots. It’s statistically a “low danger” area of the ice, so it isn’t a huge concern. Point shots are really only dangerous because of the great (for the attacking team) rebounds they often produce. But, shots from that particular spot on the point will most likely produce a weird rebound or one that’s easily cleared away by defenders due to the bad angle it’s at to the net. So, while it’s a bit of a concern and should be worked on a little bit, it shouldn’t be as high of a priority as some of the other spots.
Right Circle Could Be Better, Could Be Worse
As for the right circle on the ice, the Bruins defend at about the league average for most of it. That’s not bad, but it could always be better. Who wants to be average when you can be above average? Thankfully, there are also a few random blue spots (albeit light ones) in the “medium danger” trapezoid. This likely means that they’re right at the top of the league average, right on the edge of being slightly above average. That’s obviously a good thing.
However, in the “low danger” portion of it, there’s a sizeable red spot. But, it’s a light red, meaning they aren’t too much worse than the league average from there. Plus, it’s statistically a “low danger” area for initial shots, so it’s not that big of a deal. Plus, it’s at a weird angle to the net, which means there won’t be good rebounds from it. So, it’s really not that big of a deal. Obviously, it’d be nice if they’d work on it a bit, as you can never defend too well. But, they can’t possibly defend at or above the league average all over the ice. If there’s such a thing as a good spot to defend worse than league average, that’d be one of the big ones (same would be true of the left side, but the Bruins are good there).
Right Point Needs Work
The Bruins are significantly below average in shot suppression or blocking shots coming from the right point. That’s not good. While point shots on their own are not particularly dangerous, they often produce big rebounds that are. Shots from that far away are extremely hard for a goalie to control. So, they often pop out in what end up being perfect spots for an opponent to pounce on and bury before the goalie has a chance to reset. Rebounds are the most common way goals are scored, so gifting them to the other team is not a good idea.
If the Bruins are going to pick any particular area to work on defending better, it needs to be the right point. It apparently didn’t hurt them that much in the regular season, as they had the fewest goals against in the entire league for the entire season. But, in the playoffs, that could get exposed, as teams have more time to figure out their opponent’s weaknesses, and they’ll surely notice it and take advantage of it. So, it’s something that should really be worked on before it starts to cost them.
In short, the Bruins did a lot good defensively this season. That’s not surprising given they led the league in the fewest goals against for the entire season. They deny the shots at a rate of five fewer a game (on average) for much of the slot, which is absolutely incredible. ’re They’re also strong in the left circle, as well as parts of the left point, albeit at not quite as strong as they are in the slot. But, it’s not quite as big of a deal there, as it’s statistically a lower danger area of the ice.
On the other hand, the right side of the ice could use some work, most notably the right point. If they don’t improve the right point at least, it will most likely be exposed in the playoffs, and they’ll end up paying for it. So, hopefully they work on it. As for the rest of the right side, even though they’re largely league average there, it would benefit them to improve. You can never defend too well. Although that being said, it’s impossible for them to defend above league average (or even at the league average) all over the ice. So, it’s expected that they have some spots where they aren’t as good.
But, overall, the Bruins were excellent defensively this season. They did a great job of defending the most dangerous areas of the ice with the exception of the right point. If they can improve that, they’ll be even harder to score on these playoffs than they were in the regular season. That should seriously scare any team who may have to play. But, for us as Bruins fans, it’s certainly a wonderful thing.