"I've decided to take a break from football to address my mental health," Knight wrote on Twitter on Thursday night. "Although it was a difficult decision, it was a necessary one to be back home with my family. I look forward to returning next season."
Knight, 24, was claimed by the Ravens on Monday after he was waived by the Dallas Cowboys. Baltimore placed him on the reserve/did not report list on Wednesday.
The Ravens were looking to add depth at offensive tackle because Ronnie Stanley needed season-ending ankle surgery for the second straight year. Knight had started 10 games in three seasons with Dallas.
On Wednesday, Ravens coach John Harbaugh said he didn't know the details of why Knight failed to report, saying it was a personal matter.