The Boston Bruins have one of the best defensive pairings in the NHL with Charlie McAvoy and Matt Grzelcyk giving head coach Bruce Cassidy an excellent blend of offensive skill, playmaking talent and puck-moving ability.
So, why is not a foregone conclusion that this tandem will remain intact when the puck drops for the 2021-22 regular season opener Oct. 16?
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Here's what Cassidy told reporters on a conference call in early August after the B's signed free agent defenseman Derek Forbort.
"We know (Grzelcyk) and Charlie can play together,” Cassidy said. “Didn't work out as well in the playoffs as we'd like. It's a lot of demands on Grizz, so we brought in a guy like a Forbort that's a bigger defender than Grizz and a different type of defender. So we want to see how that would look with Charlie. Now whether we do that every night or not remains to be seen. That's a big ask.
“We know Grizz can slot in there at times, so I think you'll see some toggling. We did not see (Mike) Reilly with Charlie and probably won't. I think he was a good fit with both (Brandon) Carlo and (Connor) Clifton. So I think we're going to see those guys move up and down a little bit -- Forbort and Grizz with Charlie and see how it best works.”
Cassidy didn't say Forbort will definitely play with McAvoy, or that it would be a permanent thing, but clearly there's interest in seeing how that pairing would work out.
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One weakness for the McAvoy-Grzelcyk duo is it doesn't feature a ton of size, and that was a problem in the second-round playoff series loss to the New York Islanders last season.
The Islanders' relentless forecheck eventually wore down McAvoy and Grzelcyk. There were other factors contributing to that, too, including these two defensemen having to play a larger-than-ideal amount of minutes because of injuries to fellow blueliners Brandon Carlo and Kevan Miller.
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It's important not to overreact to one series, though, especially after the Bruins added a ton of depth to their roster over the summer in free agency.
From an offensive and puck possession standpoint, the McAvoy-Grzelcyk pairing ranked at or near the top of the league in several key statistical categories among duos with 300-plus minutes played at 5-on-5 last season, as seen in the chart below:
| Stat (via Natural Stat Trick) | McAvoy-Grzelyck | NHL Rank |
| Shot Attempt % | 63.56 | 1st |
| Shots Against | 109 | 2nd |
| Shots For % | 68.31 | 1st |
| Goals Against | 4 | T-2nd |
| Goals For % | 74.07 | 2nd |
| Scoring Chances Against | 101 | 2nd |
| Scoring Chances For % | 64.31 | 2nd |
| High-Danger Attempts Against | 37 | 2nd |
So, when the McAvoy-Grzelcyk pairing is on the ice during 5-on-5 action, the Bruins account for 68 percent or more of all shots on net, goals scored and scoring chances. That's a very, very good rate. Of course, stats don't tell the entire story. But if you want to judge by the eye test, you'll notice how efficiently the McAvoy-Grzelcyk tandem retrieves pucks in the defensive zone, skates out of trouble and jumpstarts the rush up ice. The chemistry between them is fantastic, and much of that started while they were teammates at Boston University.
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Forbort is not an offensive-minded, smooth skating defenseman like Grzelcyk. His game is more physical, which is why he ranked fifth among defensemen with 115 blocked shots and saw regular penalty killing work for the Winnipeg Jets last season.
That said, Forbort does make sense riding with McAvoy against bigger teams or when specific matchups warrant it. It's also a good idea to get Forbort some reps with McAvoy during the regular season so they have some chemistry in case Cassidy puts them together in the playoffs. However, the Bruins aren't going to maximize McAvoy's talent or raw production if Forbort is his main partner throughout the season.
These pairings offer Cassidy a good mix of offense, shutdown defense and mobility:
Matt Grzelcyk--Charlie McAvoy
Mike Reilly--Brandon Carlo
Derek Forbort--Connor Clifton
The bottom line is the McAvoy-Grzelcyk pairing has worked so well over a large enough sample size that there's no real reason to blow it up. Why mess with success? Go with what works.