DKPittsburghSports.com reported that Reid tore the ACL in his left knee.
Penn State doesn't comment on injuries and hasn't announced a change in Reid's playing status.
Known for his copious film study, Reid started all 14 games for the Nittany Lions as a sophomore last season and was the team's leading punt returner. Reid was an all-Big Ten honorable mention selection.
Senior Christian Campbell, who started two games last year, would likely be Reid's replacement if he is out long-term.