The team is still waiting for an MRI to confirm the injury, according to the report.
Nelson hurt his left knee during the Packers preseason game against the Steelers on Sunday. He left the game after slipping on the turf during the Packers' first drive.
Quarterback Aaron Rodgers's favorite target, Nelson had 98 catches for 1,519 yards and 13 touchdowns last season. In his seven-year career, Nelson has 400 catches for over 6,000 yards and 49 touchdowns.
Nelson signed a four-year, $39 million contract with the Packers in July of last year.