CHICAGO -- Bears quarterback Justin Fields has a dislocated right thumb and is doubtful to play against the Las Vegas Raiders in Week 7, coach Matt Eberflus said Monday.

Fields suffered the injury in the third quarter of the Bears' 19-13 loss to the Minnesota Vikings on Sunday. X-rays were negative, but he had an MRI on Monday.

"There's no timetable right now," Eberflus said. "It's really going to come down to grip strength and the natural swelling that occurs with this injury, so we should know more at the end of this week."

Eberflus said he did not get any feedback on what the MRI revealed and reiterated that Fields' ability to grip the ball will be paramount in determining next steps.

Fields injured the thumb after landing awkwardly on his right arm while being sacked by Vikings defensive end Danielle Hunter on Chicago's first drive of the third quarter. As Fields was falling to the ground, he tried to flip the ball in the direction of running back Darrynton Evans.

After a visit to the injury tent, Fields walked back to the locker room with a towel over his right hand. He was initially listed as questionable to return and ruled out shortly thereafter.

Rookie QB Tyson Bagent will play in place of Fields if he is officially ruled out for Sunday.

Eberflus said right guard Nate Davis suffered a high ankle sprain against the Vikings and will not play against the Raiders. Cornerback Terell Smith, who was downgraded to out last Friday with an illness, will be sidelined "three to four weeks" with mononucleosis, Eberflus said.