DENVER — Heading into Wednesday's critical matchup in Colorado, it was fair to wonder if goalie Petr Mrazek had played his last game for the Flyers.

After being acquired from Detroit and playing superbly in his first three games with his new team, Mrazek had struggled mightily. Michal Neuvirth was back from an injury and was Wednesday's starter, and Brian Elliott was close to returning after core-muscle surgery.

And then …

Neuvirth was injured in Wednesday's second period. Mrazek replaced him and was brilliant as the Flyers, playing on back-to-back nights, outlasted the desperate Avalanche, 2-1, in perhaps their grittiest win of their roller-coaster-ride season.

Suddenly, Mrazek — who stopped all 17 shots in his 31 minutes, 37 seconds of action and survived a frantic Colorado push in the final five minutes — is the Flyers' go-to goalie until Elliott returns.

"He was huge for us," defenseman Shayne Gostisbehere said. "I don't know if any goalie likes coming in cold like that, but he stepped up in a big way for us. The last five minutes, we really needed him and we leaned on him a bit. And I think the boys did a good job, getting in lanes and blocking shots."

"Petr," defenseman Ivan Provorov said, "was unbelievable."

So was Provorov.

The second-year defenseman had scuffled recently, but he had a monster performance Wednesday: the game-winning goal, an assist, five blocked shots, five hits, plus-2. He played 30 shifts that covered 27:42, the first time he has surpassed the 20-minute mark since Dec. 23.

The Flyers overcame lots of obstacles, including losing their goalie after he looked razor-sharp before suffering an apparent groin injury. The Flyers said they would have a medical update some time Friday, but Neuvirth could be finished for the season.

Fatigued from playing on consecutive nights and huffing and puffing because of the altitude change in Denver, the Flyers looked spent in the final five minutes as the Avalanche spent most of that time in their offensive end, buzzing around the net and firing shots from all angles.

"I'm not going to lie. We definitely felt it out there," Gostsibehere said of the altitude change. "It's definitely different."

The Avs, who began the night one point out of a Western Conference playoff spot, swarmed the net in the latter stages as the exhausted Flyers were in a defensive mode.

"Those last five minutes felt like 15," Mrazek said. "But lots of blocked shots in front of me and a couple of lucky bounces."

The Flyers threw their bodies at shots all night, finishing with 33 blocks, a franchise record since the stat became official in 1997.

"Just a gutsy effort," coach Dave Hakstol said after the Flyers greatly improved their playoff chances in the crowded Metropolitan Division and wild-card races. "It's no easy task coming in here on a back-to-back, but our guys never look for an excuse. I thought everybody that was in the lineup went out and did their part.

"Guys sold out and blocked shots and were doing everything they could."

The Flyers went 1-0-2 on the road trip through Pittsburgh, Dallas and Denver, giving them points in seven straight games (4-0-3). They began the journey with tough overtime losses to the Penguins and Stars.

"We didn't really get what we wanted to in Pittsburgh or Dallas, but I thought we played well in those games," Provorov said. On Wednesday, "I thought we played all 60 minutes and everybody battled hard and played for each other, and that's why we got the two points."

Since Feb. 3, the Flyers have points in 21 of their In their last 27 games (15-6-6).

Breakaways

Andrew MacDonald led the way Wednesday with seven blocked shots, followed by Provorov, Gostisbehere, and Jordan Weal with five each. … The Flyers are 8-5-2 in the second half of back-to-back games, including road wins over such tops teams as Tampa Bay, Washington, and Vegas. … The Flyers have four games left, including three at home. They will host Boston on Sunday, play at the Islanders on Tuesday, host Carolina on Thursday, then finish the regular season April 7 against the visiting Rangers. Of those opponents, Boston — which could meet the Flyers in the first round — is the only team that will make the playoffs. … Matt Read had five shots and excelled on the penalty kill Wednesday. The Flyers were 3 for 3 on the PK and are an impressive 14 for 16 (87.5 percent) over the last eight games. … Claude Giroux's first-period goal Wednesday gave him 93 points, equaling his career high.