Top draft pick
Upshaw suffered a shoulder strain in Thursday's final preseason game in St. Louis, his second shoulder injury of the preseason.
"Yeah, I'm concerned," Head Coach John Harbaugh said. "We'll get an MRI tomorrow."
The outside linebacker missed seven consecutive practices and the first preseason game in Atlanta due to a sprained right shoulder.
He returned for the final three games and finished the preseason with four tackles and one sack. He had one tackle Thursday night in St. Louis.
While many fans and pundits assumed Upshaw would help offset the loss of reigning Defensive Player of the Year