Kyle Allen, an undrafted free agent, has gone 4-0 as the starting quarterback in Newton's absence.
Panthers coach Ron Rivera on Tuesday said team doctors haven't told him Newton is ready to practice. Rivera also said he won't address the quarterback situation until Newton is 100 percent.
"Until he's 100 percent, until he's ready to roll, we're not going to address it," Rivera said. "He's been around. We just don't want him standing on the sideline for 4 hours for no reason. We didn't want to take him on an 8-, 9-hour flight [to London last week]. People need to understand the man has done everything we've asked. I'm trying to stay true to what I told him. I'm not going to put that kind of pressure on him.
"Until we have it confirmed with our doctors, we're going to continue to do what we're doing."
Rivera emphasized multiple times that he doesn't want Newton to feel any pressure to come back any sooner than he has to.
"I'm not sure why people want to put pressure on a guy and get him out there before he's ready to play," Rivera said. "...That's why when we sat down, I talked to him and told him, 'Cam, when it's time [to return], you're really the only one that knows it.'
"So we'll go from there. At the end of the day, we're focused on the now."
Allen has completed 65.6% of his passes for 901 yards with seven touchdowns, no interceptions and a 106.6 quarterback rating, which ranks fifth in the NFL behind Russell Wilson, Patrick Mahomes, Kirk Cousins and Deshaun Watson.
Newton struggled through the first two weeks of the season before a mild Lisfranc sprain shut him down. He completed just 56.2% of his passes for 572 yards with one interception in losses to the Rams and Buccaneers.
The Associated Press contributed to this report.
Has Newton lost the Panthers' starting QB job?
Chris Mortensen questions whether Ron Rivera is committed to starting Cam Newton once he is able to return from his foot injury.