That's good news for the Panthers, who view Benjamin as a key component in this year's offense.
Benjamin has been running with the starters at training camp.
He has been catching everything in sight and trying to adapt to quarterback Cam Newton, who is coming off an ankle injury. Rivera said Benjamin needs as many reps as possible being a rookie.
"He's had a great camp," Rivera said. "He came in in tiptop shape and ready to roll. He's one of those guys who spent time with Cam (before training camp) working out."
Rivera said Benjamin injured the knee on Sunday when he "bumped knees" with another player.
Benjamin finished the practice and Rivera mentioned nothing about the injury after practice. When Benjamin reported for treatment on Monday morning, trainer Ryan Vermillion decided to send him to Charlotte, North Carolina to have an MRI as a precautionary measure.
Benjamin was the 28th overall player drafted.
He caught 54 passes for 1,011 yards and 15 touchdowns last year for Florida State, including the winning touchdown against Auburn in the national championship.
NOTES: The Patriots claimed running back Tyler Gaffney on Monday, one day after the Panthers waived the injured rookie. Gaffney was Carolina's sixth-round draft pick this year.