Explaining Advanced Stats: Fenwick Close

Many of our readers may be aware of the “advanced stats” paradigm shift taking place in hockey analysis recently with statistics like Corsi and Fenwick becoming more mainstream for armchair analysts like us here at Stars and Sticks. Still, these statistics are relatively new and can take some getting used to. In part one of our series explaining some of the statistics we use to analyze the Caps and the rest of the league, we cover Fenwick Close today and how it can be a useful tool in breaking down the game.

To understand Fenwick Close we first have to get a handle on what Fenwick is. You’ll notice that Fenwick is typically expressed in terms of percentages, so here is the textbook definition of Fenwick % via war-0n-ice:

"Fenwick%: The percentage of unblocked on-ice shot attempts (on goal or missed) taken by the player’s team; also known as FF%"

Simply put, Fenwick is similar to the easy-to-understand “shots on goal” statistic, but it also takes into account unblocked shot attempts that miss the net as well as those which are registered as classic shots on goal. Let’s take the Caps’ win over the Blue Jackets last night as an example, where the Caps won the Fenwick battle with 54.32% Fenwick in their favor, meaning they had 54.32% of unblocked shot attempts in the game.

With me so far? Good.

So now that we (hopefully) have a grasp on the Fenwick concept, Fenwick Close simply measures the percentage of unblocked on-ice shot attempts directed on net in close-game situations. For Fenwick Close, the definition of a close situation is when the score differential is one goal or less in periods one and two, and a tie game situation for the third period.

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Why is it useful?

Fenwick itself is useful because it’s one of the best approximations we have to measure puck possession. It stands to reason that the team which has the puck more often will direct more shots at the opponent’s net than the other way around. The modern day NHL is much more of a puck-possession game than it used to be in the 90’s. L.A. Kings Coach Darryl Sutter said it best with this quote earlier in the year:

"“The game’s changed. They think there’s defending in today’s game. Nah, it’s how much you have the puck. Teams that play around in their own zone they they’re defending but they’re generally getting scored on or taking face-offs and they need a goalie to stand on his head if that’s the way they play,” said Sutter."

There is a strong correlation between puck possession metrics such as Fenwick and team success. In case you missed this chart in my “don’t panic” article about the Caps last week, here it is again. The relationship between possession and playoff success is direct and positive.

Mandatory Credit: Habs Eyes on the Prize blog (SBNation)

So now that we understand Fenwick, why is it important to use Fenwick close?

Fenwick close is a useful stat because it accounts for score effects, which are an established statistical phenomenon in hockey. Namely, when a team trails by two or more goals in the first two periods, they tend to have a surge in possession numbers. Same goes for a team that trails by only one or more in the third. It’s why the old hockey adage exists about the two goal lead being “the most dangerous in hockey.”

Why does it happen? Usually it’s a combination of the fact that teams with a lead naturally let up and teams that are trailing tend to expend more effort and energy to catch up. It’s part of human nature.

Fenwick close eliminates big lead and blowout situations which would throw off the Fenwick statistic and skew it in a way that might not be informative. Let’s use a real life example to describe how it might work: on Tuesday night the Rangers beat the Penguins 5-0. Here’s the Fenwick chart from that game:

Mandatory Credit: www.War-On-Ice.com

This Fenwick chart represents Fenwick (Y-axis) over time (X-axis) throughout the game. The blue line graphs Rangers shot attempts, the gold Penguins shot attempts. The Rangers’ goals are marked by the vertical purple lines. Notice anything?

Look at how the Rangers’ Fenwick flattens out after their fourth goal and the Pens catch up and actually overtake them in attempts. Is that indicative of anything? Not really, other than the fact that the Rangers sat back with a 4-0 lead and the Pens finally started to carry the play. But if you look at just the raw Fenwick data, the Pens carried a slight advantage on the night with a 50.55% Fenwick rating. Not very informative.

However, a closer look reveals that the Rangers won the Fenwick-close battle 66% to 33%.

How are the Caps Doing?

So far, so good, according to awesome stats site war-on-ice.com. The Barry Trotz Caps currently sit 4th in the NHL in Fenwick Close with a 55.08% ranking. The Devils, who come into town Friday, are ninth worst in the league at 48.12%. That bodes well for the Caps on Friday and moving forward if they can keep it up.

Tomorrow, my esteemed colleague Dave Stevenson will break down Corsi and how it can be informative.

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