Thursday, August 28, 2014

Howard's Goals Against in RBS and QS

Today at WingingitinMotown, JJ from Kanas took a look at Jimmy Howard's number of Quality Starts and Really Bad Starts. You can check it out here http://www.wingingitinmotown.com/2014/8/28/6068191/red-wings-goaltending-analysis-jimmy-howard-quality-starts.

For those of you who are unaware, these stats come from Rob Vollman's Hockey Abstract 2014 (which I highly suggest you purchase) and are defined as
•Quality Start (QS): A performance where the goaltender put up a .917 or better save percentage or, if the opponent failed to get more than 20 total shots, a game where he stopped 88.5% or better.
•Really Bad Start (RBS): A performance where the goaltender failed to attain even an .850 save percentage.

One theory he mentions is the possibility that “Howard gets cocky after a dominant start and lets off the gas or that he gets fired up by a loss and bears down harder on the next go.” He and I are both hesitant to agree with that claim. I am hesitant mainly because simple regression to the mean explains at least part of this effect. Also, since we are dealing with the best goaltenders in the world I assume they have the ability to focus and manage their emotions, with some extreme exceptions. Supporting my theory, it has been demonstrated that no goalie is particularly streaky, at least statistically speaking (http://nhlnumbers.com/2012/5/11/the-myth-of-the-hot-goalie-consistent-goaltenders-vs-inconsistent-goaltenders) leading me to believe this is just simple variability rather than a change in concentration.

Regardless, I have slightly more information to add to this analysis since I broke down the type of goals Howard let in last season. Based on the theory I would guess in his RBS Howard lets in more clean goals, the goals over which he has the most control. While in the QS, if it is truly Howard “baring down,” we would see the opposite as he lets in less of these controllable saves.



Now all of the analysis should be taken with a grain of salt since I have only last season to work with and as a result have extremely limited sample sizes. I first separated all the goals given up in his RBS and compared how many of each type he gave up compared to how often he gave them up in total last year.

The major differences comes from a massive spike in clean goals allowed and simultaneous drop in rebound goals given up, which somewhat fits with the hypothesis that he was taking it easy. Howard was overly confident, and didn't make saves on clean shots leading to more clean goals and less rebound opportunities. Before we close this case however, I remind you of a game against Nashville directly before the Winter Classic. Jimmy Howard was particularly awful in this game, giving up 5 goals on 28 shots, the definition of a really bad start. However this also happened to be his first game back from injury, and his first start in 20 days. While the poor game could be due to his decreased focused, if we instead attribute the poor showing to rust and remove it from the data set, the numbers are far less conclusive.
Howard still sees a huge decrease in rebound goals, and a slight raise across the board, making it appear that it may simply be luck and regression causing these results. However we are dealing with a very small data set, thankfully he doesn't have many RBS, and removing a cherry-picked game made the data even smaller. So while this does seem to go against JJ's theory, I am not ready to declare his hypothesis dead just yet. Luckily, Jimmy does have a higher percentage of Quality Starts, so we can get a better look at the idea that he is more focused in those games than in the other games.


Doing the same analysis for Quality Starts as I did for Really Bad Starts we start to see where the theory fall apart. In the games where he records a Quality Start, the biggest difference is that Jimmy gives up a much smaller percentage of transition goals. While I am willing to admit Jimmy’s improved focused in these starts could lead to an increase in saves on these opportunities, I am more inclined to believe this is the result of improved defensive play. Transition goals often come from the result of odd man rushes and backdoor passes, plays where Jimmy has little control and is at the mercy of the Red Wing's defensive play. The remaining possibility would be that Jimmy plays deeper in his net due to his confidence in stopping clean shots, allowing him to more easily get to transition opportunities a la Henrik Lundqvist. However such a drastic change in ability would require a noticeable change in style, so I am more comfortable attributing this change to improved defending.

Until I have data on each and every shot attempt given up by the Wings JJ's theory is still plausible. For now I can not definitively demonstrate a change in the kind of shot attempts given up by the Wing's in different starts. Additionally, the psychology of goaltending is a topic of which I am very intrigued and I remain open to the possibility that it has an effect on play. I just received Mike Valley's book The Power Within, and hope to learn more about this topic through the reading. However, for now I think this quick analysis provides some evidence that defensive play and random variation may have more to due with quality starts and really bad starts than goaltender focus.

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