EARTH CITY, Mo. -- Already without starting guard Rodger Saffold for the rest of the season because of a shoulder injury, the St. Louis Rams likely lost their other starting guard Sunday against the Chicago Bears.

Rookie right guard Jamon Brown, the third-round pick out of Louisville, suffered what Rams coach Jeff Fisher called a fractured lower leg late in Sunday's 37-13 loss to the Bears. Early indications are that Brown also will be lost for the rest of the season.

"It doesn’t look good," Fisher said. "It looks like he’s got a lower leg fracture so he’ll probably be done (for the year)."

Brown left the game on a cart after he attempted to tackle Bears linebacker Willie Young following an interception. Fisher was unsure what exactly happened to Brown.

"You know what, I don’t know," Fisher said. "When I got over there, he was in a lot of pain. It was on the interception return. He tried to make a tackle and in those particular situations, sometimes you get landed on in the back or get your foot caught in the turf. It’s unfortunate for JB because he was off to a great rookie year."

Brown, who was the first of the Rams' two third-round picks in May, started his ninth consecutive game Sunday. Rookie Cody Wichmann replaced Brown against the Bears, though the Rams likely will decide between Wichmann and Andrew Donnal, who started at left guard against Minnesota last week, to replace Brown long term. Demetrius Rhaney is another option.

Meanwhile, Brown wasn't the only rookie Rams offensive lineman to suffer an injury against Chicago. Right tackle Rob Havenstein, who returned from an Achilles injury after missing the Minnesota game, also departed with a calf ailment. He did not return and had ice on the back of his leg on the sideline in the fourth quarter.

Undrafted rookie Darrell Williams replaced Havenstein at right tackle.

"We had Rob come out with a calf sprain so we made some changes up on the offensive line," Fisher said. "Nonetheless, it shouldn’t be a reason that we lost the game."

Regardless, the Rams will now have to do even more shuffling to an offensive line that hasn't had much success in 2015.