An injury to third-line center Nolan Patrick has clouded the Flyers’ roster decisions.

New coach Alain Vigneault said Thursday he does not know whether Patrick — who has been skating on his own but hasn’t participated in camp because of an unspecified upper-body injury — will be ready for the Oct. 4 opener against Chicago in Prague.

Patrick’s absence has opened the door for hotshot prospect Morgan Frost, who was a candidate for the third-line right-wing spot but is now viewed as a potential replacement for Patrick.

Frost, 20, was hindered by a groin injury before making his first preseason appearance Thursday, in a 3-1 loss to the Boston Bruins at the Wells Fargo Center.

He made the most of it — sort of.

Frost didn’t score, but he was in the middle of more golden scoring chances than anyone on the ice.

In the first 13 minutes, 20 seconds, Frost was robbed twice by Boston goalie Jaroslav Halak — as he tried to finish a two-on-one with Andy Andreoff, and when he shot a rebound into Halak’s glove (the goalie didn’t know he had it) with the Flyers on a power play.

Frost held his head in disbelief on the second save, which followed his deflection that kissed the right post.

Flyers center Morgan Frost skates with the puck past Boston Bruins right wing Karson Kuhlman during the first-period in a preseason game on Thursday, September 19, 2019 in Philadelphia.
YONG KIM / Staff Photographer
Flyers center Morgan Frost skates with the puck past Boston Bruins right wing Karson Kuhlman during the first-period in a preseason game on Thursday, September 19, 2019 in Philadelphia.

“I don’t know how he saved that, to be honest,” Frost said after the Flyers (0-2-1) lost to what amounted to the Bruins’ B team.

Frost centered veteran wingers James van Riemsdyk and Jake Voracek, and he was much more effective than in his lone preseason game last year.

“I just felt more comfortable going into the game tonight, especially playing with guys like JVR and Jake," Frost said. “It definitely helps with your confidence and made things a little easier tonight.”

Frost, whose team was outshot, 34-24, also had a good scoring chance midway through the second period, but he couldn’t finish.

“He had a couple good looks. I definitely can see the skill in him,” Vigneault said. "He’s got some upside."

While Frost was centering the second line, rookie Joel Farabee played right wing on the top unit, which included Claude Giroux and Sean Couturier, veteran stars playing their first preseason game this year.

“Those kids are getting a good opportunity,” Vigneault said about Farabee and Frost playing on top lines. “ … You want to put players in a situation where they’re going to have success. It does not mean that Frost may come back at some point and be on the fourth line, but right now, there’s some spots that are available.”

On defense, Ivan Provorov and Matt Niskanen were paired together in their first preseason appearances. Niskanen, from above the right circle, tied the score at 1-1 by drilling a high slap shot past Halak with 8:02 to go in the first period. Farabee caused havoc in front of the net.

“It was really good work by G and Coots down low,” said Farabee, referring to Giroux and Couturier. “They grinded it out for a bit, and then we got possession. I was able to free up some space in front of the net, and Niskanen put the puck right where he wanted it.”

With right winger Travis Konecny signed and probably ticketed for top-line duty, Farabee’s best chance to make the roster seems to be as the third-line right winger.

Breakaways

Brian Elliott played the first two periods and stopped 21 of 23 shots (. 913 save percentage). … The Flyers have managed just four goals in three preseason games. “It’s a process,” Vigneault said. “I think what you saw today was one team that knew their system, executed it without thinking, and played it well, whereas we’re a little bit in the thinking mode on the ice, and it makes us look a little hesitant. We have a lot of work to do, and we’ll do it.” … The power play is 0 for 13, and the penalty kill is 9 for 9. … Connor Clifton came out of the penalty box and beat Alex Lyon on a breakaway to give the Bruins a 3-1 lead with 3:45 left.