July 11 2012 10:12AM
A few days ago, I presented some of what we were able to learn from Geoff Detweiler's data tracking the Flyers' zone entries in 2011-12. One of the things I noted is that carrying the puck into the offensive zone generates a lot more offense than dumping the puck in.
In this article, I'll follow that observation up by answering some of the questions that a lot of people have asked and showing a little more about what we found.
Do odd-man rushes inflate the results of carrying the puck in?
Geoff noted whenever an entry was an odd-man rush because we expected them to bias the results. In the end, we found that only 290 out of 9680 even-strength zone entries were on an odd-man rush, so we didn't even bother pulling them out in our year-end review on Broad Street Hockey.
However, it's been a persistent question since then, so I might as well go ahead and work things out:
|Shots per entry, overall||0.57||0.56||0.25||0.26||0.53|
|Shots per entry, odd-man rush||0.80||0.74||0/0||3/2||6/6|
|Shots per entry, rushes excluded||0.56||0.55||0.25||0.26||0.53|
From this, we see:
- Gaining the zone on an odd-man rush is distinctly more dangerous than gaining the zone with even numbers.
- However, odd-man rushes are infrequent enough in today's NHL that they don't skew the numbers appreciably.
- Gaining the zone with even numbers is actually closer to an odd-man rush than it is to dumping the puck in.
Are there factors deflating the results of dumping the puck in?
One example that people often bring up is when the offense dumps the puck in and goes for a line change. We didn't log dump-and-change plays at all, only offensive plays where the team made an active effort to recover the puck after dumping it in. So those shouldn't be a factor.
Another notion that comes up a lot is that dumping the puck in is often the last-resort option on a well-defended play, and of course you expect to see fewer shots on a well-defended play. The response to this is that a lot of the deflections are designed plays, where you have a long dump-in with a deflection near center ice to cancel icing, and those plays don't look appreciably better than dump-ins. Besides, if the defense is challenging the blue line hard to prevent the carry-in, one might reasonably expect that to be a play where there is more room for a dump-in to succeed, not less.
It's also often suggested that bottom-six players are coached to just dump the puck, and so dump-ins look worse than they are because those plays are predominantly executed by lesser players. It is definitely true that the less-skilled players dump the puck in more often. However, the thing that was shocking about the first pass through this data was that the skilled players do not do appreciably better with the entries they get:
|Player||% with possession||Shots per carry/pass||Shots per dump/deflect|
The Flyers' fourth line (Couturier-Talbot-Rinaldo) averaged 0.29 shots per time they dumped or deflected the puck in, while the top line (Giroux-Jagr-Hartnell) averaged 0.28. The fourth line averaged 0.56 shots per time they carried or passed the puck in, while the top line averaged 0.53.
The reason Giroux has a better shot differential than Rinaldo isn't that he does more with each entry; it's that he wins the neutral zone more often (more total entries) and does so more decisively (gaining the zone with possession).
If it's true that the less-skilled players are being coached to just dump the puck in -- and I suspect it is -- then the coach might be doing more to limit their offense than their own lack of skill is. This is the kind of inefficiency that can be identified, fixed, and exploited to gain an advantage over the rest of the league.
Yes, carrying the puck in is better than dumping it in. But if a rush is well-defended, is a team better off trying to regroup or dump the puck in?
This is a question that we can't truly answer, since no NHL teams are running that experiment for us. We know that when the Soviets tracked zone entries, they decided that regrouping was the right strategy, but this is a different era and the same strategic considerations might not hold in today's game. Let's try some math and see what we can come up with.
Dumping the puck in immediately is worth about 0.24 shots. Backing up and trying again gets you about 0.44 shots if you get the next entry (this is the average gain across all types of zone entry at 5-on-5), but if you turn the puck over it might cost you 0.44 shots at the other end. So your net shots from regrouping will be (0.44) * (odds you get the next entry) - (0.44) * (odds your opponent gets the next entry). As a result, regrouping turns out to be unfavorable if there's a 23% chance your opponent will eventually get the next entry after you back up.
That sounds grim for the regrouping strategy, but it's not as bad as it sounds:
- If you turn the puck over, the opponent won't automatically advance it into your zone; they might still turn it over again or need to dump-and-change, giving you another chance.
- The 0.44 shots per entry figure is the average for everyone, but some lines carry the puck in on more of their entries and therefore get more shots per entry.
- The lines with the puck skills to carry the puck in more are also the lines least likely to turn the puck over in the neutral zone after they regroup.
It works out that if Giroux's line is going to turn the puck over less than 1/3 of the time after regrouping, regrouping will probably be advantageous. If I were a head coach, I would definitely run some drills to see whether they can beat that number.
Pressing every opportunity
Even setting aside the idea of regrouping, our data can impact strategy. The difference between offense generated on a carry-in and a dump-in is quite large. This makes me suspect teams aren't trying hard enough to press their marginal edges and carry the puck in on borderline plays.
However, I can't prove that teams aren't being aggressive enough, since we only know the overall average for carry-in plays and not specifically how those marginal plays go. For example, a distribution like this would support the current approach:
|Hypothetical carry type||Hypothetical carry frequency||Hypothetical carry generated|
|Odd-man rush||6% of carry-ins (known)||0.79 shots apiece (known)|
|Poorly defended||35% (hypothetical)||0.7 shots apiece (hypothetical)|
|Typical||40% (hypothetical)||0.55 shots apiece (hypothetical)|
|Well defended||19% (hypothetical)||0.3 shots apiece (hypothetical)|
This is a plausible hypothetical situation -- it matches our known odd-man rush results and gives the known average shots per carry in overall (0.57). And it has those marginal well-defended situations close enough to what a dump-in achieves that if this were what actually happens in the NHL, there would be no reason to press harder on the marginal plays.
However, although this distribution is plausible, it doesn't look very likely to me -- it has the "poorly defended" group being so poorly defended that those plays are almost like an odd-man rush, and yet they are still twice as frequent as a well-defended play. Yet one has to invoke a distribution this skewed to defend the current strategic approach.
In other words, I can't prove that teams should be pushing the marginal chances to carry the puck in harder than they are, but it seems very likely. And it would be consistent with findings in many other sports that strategies tend not to be aggressive enough (stealing a base to try for one run instead of playing for a big rally, punting or kicking a field goal on fourth down instead of trying to extend the drive, hitting a soft second serve to avoid a double fault instead of trying to keep the opponent on their heels, etc).
Carrying the puck in is way better than dumping it in, more than twice as good -- and it's not because of odd-man rushes or player skill or any other external factor; it's just because having the puck in the opponent's zone headed towards the goal is a lot better than trying to outrace the opponent to try to get the puck in the corner.
Most people don't recognize just how big the difference is, and the data suggests that teams should be trying harder than they are to carry the puck in. If coaches are telling their third line to dump the puck, they are probably giving away scoring chances. If coaches are telling the players to dump the puck in borderline situations where they think carrying it might lead to a turnover, they are probably giving away scoring chances. Even regrouping and trying again might be better than dumping the puck in, especially when the team has their top line on the ice.
Finally, while Geoff's data has been extremely helpful in breaking down the Flyers' performance this year, our conclusions will be a lot stronger when we have multiple teams to compare. If you're interested in joining this project, let me know (bsh.erict -at- gmail or @BSH_EricT) and I'll forward the templates we've used so you can track games next year or make a summer project of going through last year's games on Game Center Live.
[Data on odd-man rushes are corrected from original version to remove six spurious entries.]