Bruins rookie Austin Czarnik was not present at Monday’s practice at Warrior Arena after taking a hit to the head from Flyers defenseman Radko Gudas during the third period of Saturday’s preseason finale.

“Obviously it was a shoulder-to-the-head injury,’’ Bruins coach Claude Julien said. “He’s day-to-day as you go through concussion situations there, so we’re just being cautious with him and see where he goes.’’

Czarnik, a 23-year-old forward, scored two goals and notched one assist in six preseason games while vying for a roster spot.

Gudas was whistled for boarding after the hit on Czarnik, who was helped off the ice and into the dressing room. He did not return to the game.

Gudas had a telephone hearing with the NHL Monday and was suspended six games. He is a repeat offender and served a three-game suspension last season.

Earlier in the preseason, Gudas hit Rangers rookie Jimmy Vesey and was ejected after receiving a five-minute boarding penalty and a game misconduct. He was not suspended for the hit.

Riley Nash skated with Matt Beleskey and Jimmy Hayes during Monday’s practice, and Julien said he could be among the options to center that line if Czarnik is unable to start the season Thursday.

“I think he’s very capable of filling in that spot, as others,’’ Julien said. “We just put him in there today for the sake of having four lines and seeing what he gives us if we have to go without Austin there. We’ll see.’’

Ehrhoff released

The Bruins released Christian Ehrhoff from his professional tryout agreement, according to general manager Don Sweeney.

The Bruins invited Ehrhoff to training camp to compete as a depth defenseman after he played for Team Europe in the World Cup of Hockey. Ehrhoff, 34, was trying to follow the route taken by ex-Bruin Dennis Seidenberg, who played well enough during the tournament to earn a one-year $1 million contract with the Islanders.

Ehrhoff was present at practice Monday. But the Bruins spent the session working on special teams play, and he saw little ice time.

Ehrhoff appeared in three preseason games, including Saturday’s 1-0 overtime win in the finale against Philadelphia.

“It was a chance to prove I can still play in this league,’’ Ehrhoff said after the game. “I just took it day by day and tried to do my best out there. That’s what I did. I put it all out on the line.’’

Ehrhoff played in 48 games last year with the Kings and Blackhawks. His release leaves the Bruins with nine defensemen: Zdeno Chara, Colin Miller, Torey Krug, Kevan Miller, John-Michael Liles, Adam McQuaid, Joe Morrow, Brandon Carlo, and Rob O’Gara.

The team must set its 23-man roster by Tuesday at 5 p.m. McQuaid and Kevan Miller did not practice Monday because of undisclosed ailments. Carlo and O’Gara, who are eligible to be assigned to Providence, could stick with the big club, depending on the conditions of McQuaid and Miller.

Julien said that McQuaid is day to day, and that Miller will be further evaluated.

“Our two young D’s are still out there, O’Gara and Carlo,’’ Julien said. “You have a lot more, I guess, choices, and a lot more flexibility as far as that’s concerned. You talk about depth, that’s when it becomes important.

“We got a couple guys this morning in McQuaid and also Miller that aren’t on the ice so you have people coming in that you feel have done a really good job and are still here at the time we speak.’’

Waiving goodbye

The Bruins placed forwards Seth Griffith, Tyler Randell, and Tim Schaller on waivers and sent forwards Jake DeBrusk and Sean Kuraly and goaltender Malcolm Subban to Providence Monday.

Griffith, 23, skated in four games for the Bruins last season and appeared in 30 games during the 2014-15 season. He has six goals and five assists at the NHL level.

The 25-year-old Randell made his NHL debut last season and played in 27 games in Boston. He tallied six goals and logged 47 penalty minutes.

Schaller is from Merrimack, N.H., and played four years at Providence College. The 25-year-old former Buffalo Sabre was signed to a one-year, two-way contract in July.

Emily McCarthy can be reached at emily.mccarthy@globe.com. Follow her on Twitter at @emilymccahthy. Fluto Shinzawa of the Globe staff contributed to this report.