Will one of two rookie centers, Morgan Frost or German Rubtsov, replace the injured Nolan Patrick when the Flyers open their season Oct. 4?

Can bruising right winger Chris Stewart or impressive rookie left winger Carsen Twarynski earn a spot on the fourth line?

Will Robert Hagg beat out rookie Phil Myers -- who was the favorite heading into training camp -- for the No. 6 spot on defense?

Those are just some of the questions the Flyers’ brass will answer this week as the team completes the NHL portion of its preseason schedule, playing in Boston on Monday and in New York against the Rangers on Thursday.

“There’s good competition and there’s good decisions for us to make,” coach Alain Vigneault said after practice Sunday in Voorhees.

Final rosters have to be submitted by 5 p.m. on Oct. 1.

When the season starts Oct. 4 against Chicago in Prague, the first two lines might look like this: Sean Couturier centering Claude Giroux and Travis Konecny, and Kevin Hayes centering James van Riemsdyk or Oskar Lindblom, along with Jake Voracek, on the second unit.

There are several positions still open, and injuries to Patrick (upper body) and Tyler Pitlick (wrist surgery) have complicated things. Pitlick was able to practice Sunday, but has not been cleared for contact.

Here are the positions that have to be determined:

Flyers center Morgan Frost skates with the puck against Boston Bruins center Karson Kuhlman in a preseason game on Thursday, September 19, 2019 in Philadelphia.
YONG KIM / Staff Photographer
Flyers center Morgan Frost skates with the puck against Boston Bruins center Karson Kuhlman in a preseason game on Thursday, September 19, 2019 in Philadelphia.

Third-line center

This spot is Patrick’s when he returns. If he’s not ready for the opener, the top candidates are Rubtsov and Frost, though Scott Laughton, the projected fourth-line center, could move into this spot.

Rubtsov, playing his third game in four nights, looked fatigued in Thursday’s 3-1 loss to Boston, but he has had a solid camp and has shown no ill effects from shoulder surgery. Frost has shown a relentless two-way game and has been in the middle of a slew of scoring chances in two preseason games.

“Ruby’s pace has picked up during camp, and he’s giving us the impression he’s s smart player who can play a 200-foot game,” Vigneault said. “With Frosty, there’s no doubt he has a really good skill level and can create more offensively than Ruby. There’s a battle there.”

Rubtstov will play Monday, while Vigneault said there’s a good chance Frost and Joel Farabee return to the lineup Thursday.

Third-line right winger

Farabee has had a good camp but, like Frost, has not been able to finish numerous scoring chances. That will come. Andy Andreoff, who struggled in his first preseason game, but played well Thursday, is also a candidate. So is Nic-Aube Kubel, who has quietly played well and received lots of praise from Vigneault. Aube-Kubel would have to clear waivers to be sent to the Phantoms, and the Flyers may not want to risk losing him.

There is also a chance reliable Michael Raffl, projected as the fourth-line left winger, is shifted to right wing on the third unit.

Fourth-line right winger

If everyone was healthy, the fourth line projected to have Laughton centering Raffl and Pitlick. Pitlick, however, may not be ready for the opener. Stewart, who gives the Flyers some needed physicality, is in the running for this spot, as are Andreoff and Aube-Kubel if they aren’t on the third line. If Raffl ends up moving to the third line, Twarynski, who had a goal and seven shots in Saturday’s 4-1 win over the Rangers, could be the left winger on the fourth unit.

For what it’s worth, the line of Twarynski, Scott Laughton, and Stewart was superb Saturday.

Misha Vorobyev is in the mix as the fourth-line center if Laughton moves to a higher line.

Sixth defenseman

Myers has had a very good camp, but he took a step backward and struggled in Thursday’s loss to the Bruins. Robert Hagg, coming off a season in which he was among the NHL leaders in hits and blocked shots, has been steady and will give Vigneault a tough decision. Samuel Morin is still rounding into form after an injury-plagued season and appears to have fallen out of the competition. Mark Friedman and Chris Bigras have played well but seem ticketed for the Phantoms.

Starting goalie

Carter Hart has stopped all 25 shots he has faced in two preseason appearances and is the leader in the clubhouse. Brian Elliott stopped 21 of 23 shots Thursday and is close to being ready for the season. It would not be surprising if Hart played 50 to 55 games this season.

Elliott will play the full game Monday in Boston, and Hart is scheduled to go the entire way Thursday against the Rangers.