Where did things go wrong with JJ Peterka in Utah?

The Utah Mammoth made one of the biggest splashes in the 2025 offseason, acquiring JJ Peterka from the Buffalo Sabres.

Most fans couldn’t believe it. All the Mammoth had to give up was a middle-pairing defenseman in Michael Kesselring and a young, unproven forward in Josh Doan.

Precisely a year later, though, the Mammoth traded Peterka to the Boston Bruins in exchange for a pair of first-round draft picks. Doan, on the other hand, played a huge role in breaking the Sabres’ playoff drought and getting them to Game 7 of the second round.

So, where did things go wrong with Peterka in Utah?

Peterka came two points shy of 70 during his final season in Buffalo. That year, he played most of his minutes alongside Tage Thompson and Alex Tuch.

Peterka began his Utah tenure with similarly offensive players, Dylan Guenther and Logan Cooley, but it didn’t stick. The Mammoth also tried him with Clayton Keller and Nick Schmaltz, but they still weren’t satisfied.

By the end of the season, Peterka was playing in a bottom-six role — and with his size profile and skill set, he’s simply not going to be very effective as a bottom-sixer.

“I take full responsibility,” Peterka told the Boston media after the trade. “Like I said before, I wasn’t happy with the way I was playing.

“I think I just have way more I can give. With Boston, I think the fit’s going to be awesome. Obviously going to work super hard this offseason to get back to my game and to help Boston win.”

We’ve written a lot about Peterka’s defensive improvement year over year. He was on the ice for far fewer goals against this season, largely because of the expectation Utah has for everyone to be defensively responsible.

Sometimes, being in position defensively comes by sacrificing potential scoring chances.

“Overall, when the focus shifts a little bit more to your defensive side, maybe like staying back sometimes or staying under the play, maybe gets you a few less points, but you give up way less goals at the end of the day,” Peterka explained in his exit interview after the Mammoth were eliminated from the playoffs.

Board battles were part of it, too.

Utah has a number of undersized players, but regardless of size, they’re all expected to win battles. Players such as Kailer Yamamoto and Michael Carcone have made their living doing that, but Peterka is just not that guy.

Mammoth general manager Bill Armstrong mentioned after the trade that part of the reason for trading Peterka was to open roster spots for the up-and-coming young guys.

“On our side of it, there’s just more good young players coming,” he said. “I think we created a spot now for a little bit of competition where some of the young guys can jump in there and go grab it.”

If rookies are limited to fourth-line minutes, they’ll develop into nothing more than fourth-liners. They need roles in which they can thrive, and if Peterka isn’t playing to his capability in the top six, it’s wiser to let someone else have that spot.

It’s also worth mentioning that Utah has wanted goaltender Sebastian Cossa for a long time, and the Peterka trade helped them acquire him. The goalie market this offseason is lean, so it was a tidy bit of business to acquire someone who can both fill the backup role this year and potentially grow into a star in the near future.

The common belief among Sabres fans is that Peterka is lazy and self-centered. I didn’t follow the Buffalo portion of his career on a day-to-day basis so I can’t speak to that, but I can say with certainty that that wasn’t his problem in Utah.

He’s a well-liked guy in the locker room and, by many accounts, in the community. He was never anything but respectful to myself and everyone else who covered the team last year, and the fact that he makes his personal rink in Germany available to the local hockey teams when he’s not using it shows he cares.

Could he have back-checked harder on occasion? Sure — the same can be said about everyone. That doesn’t make him lazy.

“Honestly, I wasn’t really happy with the way I was playing,” Peterka said in his Bruins introduction interview. “I think I have way more to give than what I showed.”

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