Mayfield suffered the injury late in the first half of Sunday's 37-15 loss to the San Francisco 49ers.
The first pick of the 2018 draft played most of the second half, but arrived for his postgame news conference wearing a walking boot on his left foot.
"A little painful right now,'' Mayfield said after the game. "I'm not real sure exactly what it is. We'll examine that tomorrow and find out. So right now I'm managing the pain and learning to step in the boot.''
Head coach Matt Rhule was fired Monday after 1-4 start that left him with 11 losses in his past 12 games.
Mayfield's subpar play contributed to this year's slow start. He had what Rhule called a "gut punch'' pick-six near the end of the first half against the Rams and his 16.5 Total QBR is the second lowest after five games of any quarterback since ESPN began tracking the stat in 2006.
Walker, 2-0 as a starter for Carolina the past two seasons, is the only healthy quarterback currently on the active roster. Sam Darnold, the 2021 starter, remains on injured reserve recovering from an ankle sprain in late August.
Rhule recently said Darnold was several weeks from being ready just to get back on the practice field.
Meanwhile, Mayfield will seek additional medical advice to help make the best decision for him moving forward. He took a $3.5 million cut in salary when the Panthers acquired him in a trade with the Cleveland Browns in July. He entered the season with a chance to earn some of that back if he played 75% of the snap this season and earned 10 wins.