"It was to be expected," Knox told Sean Jenson of the Chicago Sun-Times. "I knew I wouldn't be able to come back for training camp or preseason, so I'm just still taking it day by day."
If healthy, Knox could return after Week 6.
"I do believe I'll be back on the field," Knox said. "It could be this season, next season, who knows? But I'm going to keep striving to get better and get back on the field."
Hardin was carted off the field after spending about 10 minutes on the ground surrounded by medical personnel. The rookie gave the thumbs-up sign as he was taken away.
The Associated Press contributed to this report.