The team was awaiting the results of an MRI on Saturday before it could determine whether the injury was season-ending. The NFL Network earlier reported the news of the biceps tear.
If it is a complete tear, Raji would need surgery and almost certainly would be lost for the season. A partial tear, however, likely would not require surgery and would allow Raji to return in a month or sooner.
Raji did not speak to reporters after the game but was seen leaving Lambeau Field with a large ice bag on his right arm.
"You have an initial exam," Packers coach Mike McCarthy said after the game. "He's pretty confident about it. That's why you do the tests. We'll see what the tests say."
Raji would be the first starter the Packers have lost to an injury this preseason. They had three players sustain season-ending knee injuries -- receiver Jared Abbrederis, offensive lineman Don Barclay and tight end Colt Lyerla -- but all were backups.
The Packers re-signed Raji this offseason to a one-year, $4 million contract after he drew minimal interest on the free-agent market. Upon his return to the Packers, who drafted him ninth overall in 2009, Raji moved back to nose tackle -- his position in his best seasons (2009 and 2010) -- and was having a productive training camp.
Raji's level of play slipped the last three seasons while playing defensive end after the Packers moved Ryan Pickett to the nose. The Packers chose not to re-sign the 34-year-old Pickett, whose contract expired in March. He remains available and has said he would like to continue his career. So would defensive lineman Johnny Jolly, who also was not re-signed, but Jolly is not a natural nose tackle.
Second-year pro Josh Boyd, a fifth-round pick in 2013, replaced Raji against the Raiders, and the Packers also used promising undrafted rookie Mike Pennel in that spot. They signed former Minnesota Vikings backup Letroy Guion in the offseason as a backup nose tackle, but he has yet to practice because of a hamstring injury.