The Flyers have a 2-1 lead over Montreal in their Eastern Conference quarterfinal series, which resumes Tuesday at 3 p.m. in Toronto.

Here are three keys for the Flyers in a critical Game 4:

1. Rediscover the power play.

This was a power play that was No. 1 in the NHL during its late-season, nine-game winning streak, clicking at 32%. Remember?

Since then, their PP is 1-for-28, including the last game of the regular season. That’s 3.6% (gulp).

The entries have been awful, and there have been too much passing and too much predictability in the setup.

Time to give it a different look, such as putting a player behind the goal line more often.

“We’re going to obviously make a couple of adjustments there,” coach Alain Vigneault said Monday. “I do think, though, if you look at [Sunday] night’s game, we were able to force the Montreal team to take six penalties. We obviously worked hard and spent time in their zone that put them in that position.”

Vigneault said that “maybe it’s my positive nature, but the personnel that we have and the way we were able to make it click in that last 20-game stretch [of the regular season], I tend to believe in these players and we’re going to find a way to make it click. Our execution right now is a little off. We need to make a couple minor adjustments.”

2. Generate speed through the neutral zone and create some odd-man rushes

The Flyers have had only a handful of odd-man rushes over the first three games of this series.

Credit Montreal’s tight checking, but remember, this a Canadiens team that had nine more losses than wins (31-31-9) during the regular season. There’s a reason for that.

3. Get the top two lines producing.

To their credit, the Flyers’ top two lines, centered by Sean Couturier and Kevin Hayes, respectively, have worked hard and contributed on the defensive end. That’s helped the Flyers take a 2-1 series lead.

That said, those lines need to start turning on the red light. Going back to the round-robin tourney, the Flyers’ top five regular-season goal scorers have yet to score in six postseason games.

Yes, the Flyers are 5-1 in those games — the goaltending and defense have been excellent — but they are living dangerously.