Monday, May 11, 2009

Bang for the puck

If there is one complaint that virtually every Red Wings fan has uttered at one time throughout their fandom, it’s that the Wings often dominate in shots on goal without dominating on the scoreboard. I know I’ve felt that frustration. So, I’ve researched every game the Wings have played over the past ten years just to see if this phenomenon is true. On a per game basis, how many shots do the Wings take per goal and how does that ratio compare to their opponents? This is what I discovered…

Shots on Goal vs. Goals

TeamShots on GoalGoals
Wings7 trillion3

The above chart tells us that the Wings take 2.3 trillion shots per goal while their opponents take just one shot per goal. I'm not 100% certain on the calculations but I’m pretty sure those numbers are fairly accurate. All kidding aside, there is the perception that the Wings have a bit of bad luck when it comes to turning shots into goals. Let’s look no further than the current Anaheim-series to see why fans might feel that way. The Wings have outshot the Ducks 223-138 and only have a 3-2 lead in the series. In games two and three combined, the Wings outshot the Ducks 83-47 and lost both games. So, what gives? Let’s dig a little deeper.

The Wings clearly dominate their opponents in “shots on goal.” They have led the NHL in shot differential in each of the past four seasons. It hasn’t been by a small amount either. On average, the Wings have outshot their opponents by nine shots per game. That shot differential is more than twice that of any other team in the NHL.

The Wings also clearly dominate their opponents in “goals.” The Wings have the highest goal differential in the NHL over the past four seasons. They are the only team in the NHL to finish in the top five in “goal differential” in each of the past four seasons. Over that span, the Wings have outscored their opponents by an average of .84 goals per game.

Since the Wings have been, far and away, the best team in the NHL in both “shot differential” and “goal differential”, then it is pretty clear that their significant advantage in shots is leading to a significant advantage in goals as would be expected. That should at least somewhat calm fears that the Wings are somehow cursed with bad luck. More shots have definitely meant more goals. However, have more shots meant the expected goal differential? Over the past four years (regular season), the Wings have averaged one goal for every 10.22 shots. Using that ratio and some nifty cross multiplication, the nine-shot advantage that the Wings have had per game over that span should yield a .88 per game goal advantage. Instead—as referenced above—the Wings have had a .84 goal advantage per game. The difference between Detroit’s expected goal differential (.88) and actual goal differential (.84) is pretty small. In fact, it does more to prove that the Wings are winning by roughly as many goals as they should be winning by based on their shot differential than it does prove that the Wings are victims of “bad luck.” These numbers are based on the regular season. I did the same calculations over the last four postseasons just in case this “phenomenon” of not capitalizing only shows up in the playoffs. The Wings expected goal differential based on their shots advantage is 1.02. Their actual goal differential was 1.05. That means that in the playoffs, the Wings are actually winning by more goals than they should be based on their shot differential. Again, though, the difference between 1.02 and 1.05 is hardly significant. Whether it’s the regular season or the playoffs, the Wings are winning by as many goals as they should be winning by. Conspiracy theorists can rest easy if for only tonight.

I’m going to happily move away from the mathematical portion of the post and begin to discuss the primary reasons why people seem to think the Wings don’t capitalize as often as they should based on their shot differentials. I’m pretty sure there are at least two factors in play. One explanation has to do with “shot quality.” All shots are not created equal. High quality shots obviously yield more goals than low quality shots. If the Wings are outshooting their opponents with low quality shots, then clearly that shot advantage will not yield much of an advantage on the scoreboard. Let’s go back to the Anaheim-series for a look at how “poor shot quality” may negatively impact expected goals. Just so we’re all on the same page, “Higher quality shots” are taken closer to the net than “lower quality shots.” Here it is in chart-form. In Game 2, the Wings outshot Anaheim 62-46 and lost 4-3 in 3OT. That game seemed to fit the bill of the classic “Wings outshoot opponent by seven trillion and still lose”-game. However, a quick look at the shot chart from ESPN Gamecast shows us the shot distribution by distance and location. Check it out (Black “X”=Shot by Anaheim; Red “X”=Shot by Detroit):

Notice that the Wings’ shots are somewhat evenly distributed throughout their zone while Anaheim’s shots trend closer to the net. In fact, take a look at the substantial difference in the number of shots each team fired from just in front of the net. That area produces the highest probability of a goal according to the goal probability chart I referenced above.

Now let’s check out Game 3 in which the Wings doubled up Anaheim in shots 46-23 and lost, 2-1:

Again, notice how many of Anaheim’s shots are right in front of the net. The Wings took 18 shots above of the circles. Anaheim took just five. The Wings took a lot more overall shots but they also took a lot more low quality shots. All shots are not created equal and games two and three certainly proved that.

It’s important not to assume the Wings are doing something wrong by firing so many low quality shots. In fact, it’s part of their game-plan. The idea that the Wings are able to fire so many shots on goal suggests that they spend quite a bit of time in the offensive zone which means they tend to dominate puck possession and, thus, games. The Wings aren’t good simply because they fire so many shots on goal. They’re good because they can fire so many shots on goal. Their opponents rarely get the opportunity to do the same.

The other explanation for why fans seem to think the Wings don't score enough goals considering their lofty shot totals has to do with faulty reasoning. The Wings almost always outshoot their opponent. In fact, in 82 regular season games this year, the Wings outshot their opponent 70 times. So, if we're expecting "shot advantage" to translate into a win, then we would've expected the Wings to win 70 games. That's 19 more games than the Wings actually won. That's 19 instances in which the Wings outshot their opponents and lost. That's 19 opportunities for fans to say, "why do the Wings always seem to outshoot their opponents and lose" not to mention the playoffs in which such instances are magnified. They can't win every game no matter how many times they outshoot their opponent.

There are games in which the Wings dominate in “shots on goal” and lose. However, based on the numbers that we calculated above, those games are the exception rather than the rule. In games in which the Wings dominate in “shots on goal” and lose, the likely culprit is “shot quality.” All in all, there’s not too much to complain about there. So, next time you’re cursing the hockey gods for keeping Detroit’s shots out of the net, remember two things, a). the Wings are probably firing low quality shots and, b). while some games don’t go as planned, most games resemble this


Mike R said...

I'm curious about the last playoff series' that the Wings ultimately LOST only. That one against Anaheim in the 1st or 2nd round several years ago in particular. That series alone won Giguere the Conn Smythe even though they lost in the finals.

Jake said...

The Wings outshot Anaheim by 13 per game and got swept in that series. Certainly, it sucks when it happens but it doesn't happen often. I would be interested to see what the "shot quality" was in that series from a Wings perspective.


Powered by Blogger