It should not have become a nail-biter.

Not with a 4-0 lead and everything going so well and the Flyers having played two of their best opening 40 minutes all season, allowing just eight shots.

But it happened.

Luckily, their top line bailed them out and Steve Downie gave them a much-needed empt-netter to secure the Flyers’ wild 6-4 victory over the Washington Capitals on Wednesday night at Wells Fargo Center.

“They didn’t play the way they wanted the first two periods and we were and that third period they became aggressive and sat back a bit,” said Flyers captain Claude Giroux.

“When we get a lead like that, we’ve got to keep it. The first two periods we were playing well and winning battles and we got away from it. We need to play 60 minutes.”

His line with Scott Hartnell and Jakub Voracek did yeoman’s work in the win with six points. Voracek and Giroux each had two goals.

Voracek’s second marker (18th overall), late in the game, gave the Flyers a 5-3 lead that would shrink again before Downie decided it with his empty-netter.

“They’re attacking and skating with speed,” said Flyers coach Craig Berube. “Making plays and working hard down low. Cycling the puck and competing. Power play, doing a good job.”

The victory kept the Flyers in second place in the Metro Division with 72 points -- two more than the third-place Rangers while dropping the Caps four points behind the pace.