In a must-win situation, the Flyers dropped a 3-1 decision (with an empty-net goal) to visiting Montreal on Tuesday night and missed a chance to gain ground in the playoff race.

Here are some observations:

Flat start

Maybe they are tired from a long, exhausting run to relevance and have run out of gas. Whatever the reason, the Flyers came out in the first period and looked like they did for too many games in the season’s first half.

In other words, they showed little energy in the opening 20 minutes.

The Flyers, in their most important game of the season, played a flat first period and fell into a 1-0 hole. They never dug out of it.

“We didn’t have a lot of urgency,” captain Claude Giroux said of the opening period. “We were going through the motions.”

Interim coach Scott Gordon disagreed.

“I think our guys were ready to play,” he said. “Montreal didn’t make it easy for us; that’s for sure. They were ready to play. They knew how big the game was.”

The Flyers have 18 wins and 19 losses (18-15-4) at home. That’s not a recipe for a playoff spot.

Sleepy attack

Montreal’s defense played sound positional hockey the entire game, but the Flyers made it too easy on the Canadiens — especially in the first 30 minutes.

For most of the night, the Habs kept the Flyers shots to the perimeter and allowed little traffic in front of Montreal goalie Carey Price.

“If he sees the puck, he’s going to stop it,” Giroux said.

“They worked pretty hard at preventing us from getting near [the net],” Gordon said. “Whether we need a little more fight or not, I wouldn’t be able to tell you until I saw the tape.”

Hart solid

Rookie goalie Carter Hart was tough on himself for the two goals he allowed, but one was a Shea Weber drive that got past him because he was screened, and the other was when Flyer-killer Brendan Gallagher got a fortuitous bounce after Christian Folin’s shot was blocked by Andrew MacDonald. Gallagher got the rebound and scored from the high slot.

“I’ve got to do a better job finding pucks through traffic,” Hart said.

Maybe. But Hart, 20, was much better than the last time he faced Montreal and allowed three goals on nine shots and was removed from that Feb. 21 game, a 5-1 loss.

This time, he stopped 33 of 35 shots.

This loss was on the Flyers’ weak attack, not on Hart.

Wasted opportunity

The Flyers used an admirable 18-4-2 run to get back into the playoff race, but they have lost three of their last four games and their postseason hopes are hanging by a thread.

The worst part: Columbus lost Tuesday in Calgary, 4-2, so the Flyers missed an opportunity to get within four points of the Blue Jackets, who hold the final wild-card spot. Instead, the Flyers are six points out with nine games remaining. Montreal is one point behind Columbus.

“We’ve got to keep battling to the end,” center Sean Couturier said after reaching the 30-goal mark for the second straight season. “Try to get on a streak here and almost win out. Hopefully, we get some help from other teams.”

First, they most take care of their own business. If they had won Tuesday and if they had not blown a three-goal lead in Toronto on Friday, the Flyers would be just two points out of a playoff spot.

Woulda. Coulda. Shoulda.

After more than two months of excellence, they have lost three of their last four games and are limping to the finish line.