Expansion is hitting the two-time PWHL champions hard.

Eight days after clinching their second Walter Cup in as many seasons, the Frost have lost their two best blue liners to the Vancouver club joining the league next season.

Vancouver signed Sophie Jaques and Claire Thompson, two of the three finalists for the PWHL’s defender of the year award, on Wednesday, the first day of the exclusive negotiating window for Vancouver and Seattle.

It’s a terrific start for Vancouver general manager Cara Gardner Morey, who recently left her job as Princeton’s head coach to take over the expansion franchise that will be the fourth Canadian PWHL team.

“That’s the nature of the deal. We were told this morning, and we were like, ‘Ugh!’ ” Frost head coach Ken Klee said. “Honestly, we were kind of hoping we’d lose only one and could protect the other one.”

The good news is that the PWHL is allowing teams that lose two players to protect a fourth, so the Frost added winger Britta Curl-Salemme to a list that already included Kendall Coyne Schofield, Lee Stecklein and Taylor Heise.

Stecklein might be the best blue liner on the planet.

“She is,” Klee said. “She’s lights out.”

Jaques’ 22 points in 25 games tied her with Ottawa’s Renata Fast for most by a defender this season, and her 0.88 points-per-game led the league. She said leaving Minnesota is bittersweet for her after winning two championships with the Frost, but Vancouver signed her to a three-year deal, a rarity in the young league.

“I’m excited about it,” Jaques said. “I just wanted to have some control, and they presented me with a good offer, and although I loved my time in Minnesota, I’m excited about it.”

Thompson, 27, finished third in points (18) among all PWHL blue liners and signed a one-year deal to play for Morey, her former college coach.With Jaques, Thompson and Stecklien, the Frost had three of the best blue liners in the world. Now they’ll have to fill two of those spots through free agency or the draft, and at least a few more. The expansion draft is Monday night, and Seattle and Vancouver will pick at least seven players from among the PWHL’s original six teams.

“It’s going to be a busy few weeks, for sure,” Klee said. “We’ve already lost two, and I know an offer has been made to at least another of our players. We’re going to lose four (players) no matter what.”

The back end will no doubt be a priority for Klee and general manager Melissa Caruso.

“We’ll figure it out,” Klee said. “We lose two but maybe we get a good one in free agency, get one in the draft, and maybe we’re right back where we were.”

Elsewhere, Hilary Knight, whose absence from Boston’s protected list was something of a surprise, agreed to a one-year deal with Seattle. Tied for the league lead with 29 points in 30 games this season, Knight has been the Fleet’s captain for two seasons and is a finalist for the PWHL’s MVP award.

“Signing Hilary Knight was an absolute no-brainer,” Seattle GM Meghan Turner said in a statement. “She’s the heartbeat of any team she joins.”