CALGARY, Alberta — Mathew Barzal took warmups and line rushes with the Islanders on Friday night before he was a shocking scratch and spent their 4-1 loss to the Flames in the press box.

The Islanders announced that Barzal was day-to-day with a lower-body injury, an exclamation point on the slew of injuries they’ve had over the past month. Barzal has arguably been the Islanders’ best player this season, with 41 points in 40 games. To lose him for any period of time would border on calamity for a team that is in the midst of a dogfight for a postseason berth.

“There was a little tweak [Thursday] night,” coach Lane Lambert said after the game. “He tried it in warmup and couldn’t go.”

Asked whether the injury could be described as minor, Lambert would only stick to the day-to-day designation.

Zach Parise said the Islanders found out at the same time as everyone else that Barzal wouldn’t be playing.

“We didn’t know that either,” he said. “We’ve had a real tough stretch of injuries and we’ve had guys fill in and do a good job filling in. And tonight was no different. Kinda have to be ready for whatever. … We’d like to get a healthy roster back as soon as we could.”

The Islanders had just been starting to get healthy. Cal Clutterbuck returned to the lineup on Thursday at Edmonton and Semyon Varlamov on Friday made his first start since Dec. 17 at Vegas. Kyle Palmieri, Adam Pelech, Oliver Wahlstrom and Simon Holmstrom are still on the shelf, and Palmieri is the only one of the four who made the trip out to Western Canada.

Barzal showed no signs of injury on Thursday during a 4-2 loss to the Oilers, when he played 18:45, including 7:38 in the third period.

His final shift ended with 49 seconds to go in the game, so it’s unclear when the injury occurred.

“Obviously he’s a big player and an important piece,” Noah Dobson told The Post. “It sucks when you miss him, [but] as a whole, as a group, it’s not a distraction at all.”

Varlamov started after missing eight games with a groin injury and struggled, stopping 17 of 21 shots.

Lambert said after the game that “a couple” of the injured players have skated on Long Island, an indicator that Pelech (head) could have done so, as he had previously been described as close to skating.

Aatu Raty sat out of line rushes, indicating that he was set to be a healthy scratch, before drawing in for Barzal and skating 8:31. It was Raty’s seventh NHL game this season; if he reaches 10, it will count as a year on his entry-level deal.

The Islanders were outscored 7-2 in first periods over this four-game road trip.