Team spokesperson Steven Drummond said the 2015 NFL MVP did not give a reason. Coach Ron Rivera also was unaware of why his quarterback did not participate.
"I just found out,'' Rivera said. "I thought he had a press conference today, but apparently not.''
Star players are required to be available to the media during the week while in season.
ESPN's Jim Trotter, who is the president of the Pro Football Writer's Association, spoke to the Panthers about Newton not fulfilling his media obligations this week. Newton and the team are aware the 2015 NFL MVP is subject to discipline if this remains an issue.
Newton, until Thursday, had participated in every required media opportunity the past two weeks since he made light of a football question from Charlotte Observer reporter Jourdan Rodrigue earlier this month.
Rodrigue took time off after the incident and was not at Newton's other availabilities. She returned to the beat for the first time on Wednesday, when Newton normally holds his weekly news conference. He also did not speak that day.
Newton was at practice on Thursday and sat in front of his locker for more than 10 minutes playing loud music during the media open locker room session.
Kuechly was at practice with a helmet and cleats, but he remains in the concussion protocol, where he was placed after taking a hit to the shoulder and neck area late in the second quarter of last Thursday's 28-23 loss to Philadelphia.
He was listed as a non-participant in practice on the injury report, despite participating in some individual drills during the portion open to the media. He did not participate in team drills during the media portion.
The injury report said concussion protocol on Wednesday, but it was changed to concussion on Thursday. A team spokesman said the change was made to be consistent with a past injury report.
ESPN's Adam Schefter, citing sources, reported on Sunday that the team does not believe Kuechly suffered a concussion. McCarthy said if a "player is diagnosed by medical staff with a concussion, he should be listed as concussion.''
Outside linebacker Thomas Davis said it was good to see Kuechly running around at practice.
"Just understanding this situation is not like the other situations,'' Davis said of Kuechly, in the protocol for the third time in as many seasons. "Seeing him bounce back as quickly as he has -- he's in a definite good place at this time. Just excited to see him walking around and healthy.''
Kuechly still has to participate in a full practice and be cleared by an independent physician to be eligible to play. Asked whether it was unlikely the 2013 NFL Defensive Player of the Year would play on Sunday, Rivera said, "We'll see.''
Kuechly missed three games in 2015 with a concussion. He was in the protocol for three games in 2016 and then held out the final three games as a precaution with Carolina out of playoff contention.
Benjamin did not practice for the second straight day, with swelling in his left knee that was surgically repaired in 2015.
"It swelled up from a shot he got the other day, so he went and saw the doctor,'' Rivera said. "We're a little bit concerned, so we'll see.''
Rivera said if Benjamin doesn't show signs of improvement on Friday then the team likely would make a roster move. Devin Funchess likely would step into Benjamin's role as the "X'' receiver, and rookie Curtis Samuel likely would see more time as the slot receiver.
Free safety Kurt Coleman saw his repetitions increased in practice after missing the past two games with a sprained knee. He was listed as limited on the injury report, but Rivera was encouraged by Coleman's progress.