Anatomy of a first-round upset

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In the pantheon of fears in sports, being the target of a first-round upset is near the top of the list. There’s little worse than being sent home early and unexpectedly, and some organizations can live this nightmare for years.

Hockey is a low-scoring, volatile sport susceptible to upsets. It’s part of what makes it so captivating. Yet we know talent does prevail long-term – look no further than what the Tampa Bay Lightning have done in recent years, or a handful of other brief dynasties predating them.

As we head into the 2021-22 Stanley Cup Playoffs, a question arises: Are there statistical indicators of a team’s likelihood of being upset against an inferior opponent, and if so, what are those measurements?

To analyze this, I started with the trailing 10 years of first-round playoff performances. Teams that advanced as the stronger seed from Round 1 were differentiated from teams that were upset in the opening round. I focused on the usual key performance indicators for the time being – goals and expected goals (shots adjusted for quality), stop rates and save percentages, with those numbers split across the varying game states.

Here’s what the macro data looks like:

There’s very little daylight in some of these measures, in large part because we are talking about playoff-calibre teams that aren’t separated by much in terms of talent. But there are a handful of notable observations from the data set.

- Offensive production matters, and that trend is only increasing with higher scoring. But look at the delta between expected goal scoring and shooting percentage, either at even strength or on the power play. Teams that generate heavy volumes of offensive production are smiled upon; teams that rely on