School officials announced the injury on Tuesday.
The senior battled shoulder injuries earlier this season and left the game Saturday in the first half. Lucas emerged after halftime with his right arm in a sling.
Lucas was one of Penn State's most dependable players, fourth on the team with 56 tackles. He's also one of the team's most outspoken players. He had appeared in 40 consecutive games before missing a game against San Diego State with a shoulder injury. His 33 career starts are second only to quarterback Christian Hackenberg.
Lucas switched from cornerback to safety before the season and had been splitting snaps with junior Malik Golden. He finishes his Penn State career with 180 tackles, 25 pass breakups, three interceptions and four sacks.