The Sun, citing a source, reported that an MRI on Pierce's knee revealed no major damage. A source told ESPN.com's Jamison Hensley that the second-year backup could miss practice time this week and it's undecided whether he will play in Thursday's preseason game against Atlanta.
Ravens coach John Harbaugh spoke to reporters on Saturday, but wouldn't disclose specifics on Pierce's status.
"No comment on any injury situation," Harbaugh said. "If something's serious, I'll let you know. I'm not going to get into every little nick and bruise that happens. If it's serious, I'll let you know."
Pierce rushed for 532 yards last season as Ray Rice's main backup.
Information from ESPN.com's Jamison Hensley was used in this report.