Where and when does momentum matter in NHL playoff games?

Momentum.

It’s a word we hear a lot during the Stanley Cup Playoffs, far more often than we do during the regular season. If you’ve watched all 16 games in Round 1 so far, you’ve probably heard “momentum” discussed several or even dozens of times per game.

Sometimes in sports, however, proclamations are made without being substantiated with data.

We’ve arguably already established that momentum does not really exist game-to-game during the Stanley Cup Playoffs. Six of eight series are tied 1-1, after all.

But does it exist within each game? I believe the answer is yes.

How do we define it?

Momentum is up for grabs. The penalty kill can steal it by scoring shorthanded, stifling the power play, forcing them to reload 200 feet from the offensive zone. Penalty-killing success can create frustration — and that may be a big swing, because the players you are frustrating are typically the opposition’s stars. I think there is a clear link to frustration created on the penalty kill that bleeds over into ensuing 5-on-5 play.

We heard Toronto Maple Leafs coach Sheldon Keefe mention after Game 1 against the Tampa Bay Lightning: “The five-minute major? No problem. In fact, turned it into a positive with the chances we were able to generate.”

There is something called “momentum probability,” and we’re not talking physics here — because that is out of my depth. I’ll reserve that for my wife and her honors degree in biochemistry.

But to simplify it for hockey, momentum probability would be the probability of riding the momentum wave after a special teams sequence — and it’s something that can steal a game or even a series.

The best example of this is last year’s run to the Stanley Cup Final by the Montreal Canadiens on the wave of their penalty kill. They killed penalties at a playoff-best 91.8%. But when you factor in the four shorthanded goals that they created over their 22-game run, that bumped their net penalty killing percentage all the way to 98.4%. That’s nearly flawless.

But I think we get bogged down by the special teams numbers overall. You see them flashed up on the screen whenever a team goes to the power play for the first time in a game — that one team’s unit was ranked 17th in the league and the other was ranked eighth, and so on.

We also hear that, in order to win in the playoffs, your power-play and penalty-kill units must be near the top of the league. I don’t know that is necessarily true. Regular-season success on special teams does not always carry over to the playoffs. Some teams surpass regular-season results, while others see their numbers fall off a cliff.

When playing the same opponent in a seven-game series, there are no secrets.

I went back and looked at the playoff percentages for the final four playoff teams over each of the last five postseasons. I noted where they ranked, then did the same thing for the regular season to see if those teams met expectations: