The Rangers have faced their fair share of curveballs throughout the hectic 2020-21 NHL season, but Wednesday brought a four-seam fastball.

And the Rangers bashed that 99-mph heater out of the Garden and into the Hudson River.

Roughly 2½ hours before the puck dropped in their rematch against the Flyers, the Rangers announced their entire coaching staff had to enter COVID-19 protocol and was unavailable to participate in the game.

But it didn’t matter who was behind the bench as the Blueshirts clobbered the Flyers 9-0 for their first win over Philadelphia in regulation this season. It was their third shutout of the season, and second in the past three games, while their nine goals counted as a new season high.

The Rangers posted a shutout win by nine or more goals for the seventh time in franchise history and the first time since March 31, 1986. Their seven-goal second period also counted as a single-period season high, which was one shy of the franchise record set in 1971.

Mika Zibanejad recorded his fifth career hat trick and dished out three assists, while Pavel Buchnevich cleaned up with two goals and two assists.

Alexandar Georgiev pitched his first shutout since his first start of the season, on Jan. 16 against the Islanders, turning aside all 26 shots he faced.

Rangers head coach David Quinn and assistant coaches Jacques Martin, David Oliver, and Greg Brown all were unavailable for the game, so the AHL Hartford staff filled in. Wolf Pack head coach Kris Knoblauch and associate coach Gord Murphy found themselves back behind an NHL bench for the first time since they were both fired by the Flyers in 2018-19.

“It’s been busy,” Knoblauch said of how his day had gone after the win, which improved the Rangers to 12-12-4. “I had practice with my team at 10:30 a.m. and I got pulled off about 11:30 a.m. I got the message saying, ‘Call [associate general manager Chris] Drury ASAP.’ And usually when I hear that it’s not good, it’s usually taking players away from our team, but I got the call that said, ‘Just be on standby you might be coaching [Wednesday night].’

“It was confirmed maybe one o’ clock that I was going to coach.”

Knoblauch said he and Quinn exchanged six phone calls throughout the day, but there wasn’t much for the second-year Wolf Pack coach to do because the game plan had already been worked out by the official coaching staff.

The Rangers learned of the situation Wednesday morning. And considering Rangers forward Phil Di Giuseppe has been on the coronavirus protocol list since Sunday, the team wasn’t sure if the game would still be on.

“We found out coach had a positive test,” said Buchnevich, who scored twice in the span of two minutes to open the second period. “Everybody didn’t know what was going on and what was going to happen.”

Placement in the COVID-19 protocol could mean a player or coach was deemed to have had high-risk close contact with someone who did test positive. It could also be for any other precautionary reasons.

But since Buchnevich and Adam Fox were reinstated into the lineup Wednesday following two days in coronavirus protocol, presumably due to false positives, the rest of the team was cleared to play.

“I found out [Wednesday] morning that I was cleared to play,” Buchnevich said. “I don’t know what is going on there, I have the antibodies.”

In contrast to the Rangers, the Flyers were sluggish. Goaltender Brian Elliott was pulled after the Rangers made it 5-0 off Jacob Trouba’s first goal of the season just 7:30 into the second period. Carter Hart, Philadelphia’s usual starting netminder, couldn’t stop the bleeding either as he was lit up for four goals — including all three of Zibanejad’s — on 10 shots in the second period alone. Filip Chytil added one more for good measure in the final seconds of the second period as the crowd at the Garden chanted, “We want 10!”

“I have no words, to be honest,” Georgiev said. “It was sort of surreal.”