LAKE FOREST, Ill. -- Chicago Bears rookie safety Jaquan Brisker underwent surgery for a broken right thumb, a source confirmed to ESPN.

Bears coach Matt Eberflus did not specify a timetable for Brisker's return but expressed optimism that the safety will be available for Chicago's season opener against San Francisco on Sept. 11.

"We're hopeful that he'll be back," Eberflus said. "We'll find out here shortly, so we're hopeful."

Brisker sustained the injury during the Bears' preseason opener against Kansas City on Aug. 13, a game in which he recorded four tackles, including one tackle for loss, and had a near interception. He did not practice Monday or Tuesday and was not available to play in the Bears' second preseason game at Seattle.

"It was a situation where he just woke -- sometimes you wake up with these hand injuries and it just shows up," Eberflus said. "It feels like you just kind of tweaked it a little bit and all the sudden the next day there it is."

Brisker was drafted 48th overall and is expected to start opposite veteran safety Eddie Jackson. The rookie has stood out during training camp for his contributions in the secondary and has been replaced by DeAndre Houston-Carson until he returns.

NFL Network first reported news of Brisker's surgery.