LAKE FOREST, Ill. – One day after dropping the season opener at San Diego, the Chicago Bears might have lost defensive leader Mike Brown again.

An MRI exam Monday revealed the safety suffered a serious left knee injury. Defensive tackle Dusty Dvoracek also seriously hurt his left knee.

Coach Lovie Smith would not confirm a report on the NFL’s official Web site that they would miss the rest of the season. But he did say: “They both have serious knee injuries.”

“I’ll give you some other information later on,” Smith said. “Right now, in a situation like this, I’d like to talk to the players first. I’m sure you guys can understand that. Then, I’ll let you know after that.”

If Brown’s injury is season-ending, it would be his third in four years.

It happened in the fourth quarter of Sunday’s 14-3 loss on a shot from Chargers fullback Lorenzo Neal. A team captain and former Pro Bowl pick, Brown limped toward the sideline.

Dvoracek, a starter after missing his rookie year with a foot injury, went down shortly afterward.

With Brown and Dvoracek out, Smith said safety Danieal Manning and defensive tackle Darwin Walker would start Sunday against Kansas City.

“Mike has gone through a lot,” Smith said. “He’s our team leader, great guy, competitor. We all feel for him. If I continue to talk about it, I could get emotional just knowing what Mike Brown has gone through to get himself back in position to play.”

Although he’s signed through 2008, the 29-year-old Brown’s future with the Bears could be in jeopardy. His string of injuries started in 2004, and just like the two that ended seasons, this one came after he delivered a big play.

Brown’s interception of Philip Rivers’ pass and 27-yard return in the first quarter Sunday set up Robbie Gould’s field goal.

“It’s another sad day in the chapter of my football playing career, it looks like to me,” Brown told reporters on Sunday, when he broke into tears in the locker room. “I don’t know what else to tell you guys.”

Smith sidestepped questions on Monday about the play involving Neal, saying: “There probably should have been penalties on a lot of plays out there that happened on the football field – on them and on us. The officials did a good job. You can’t get everything.”

Will the Bears send video of that play to the league?

“Every play that we feel is missed, we send to the league,” said Smith, who would not say if that play was one of them.

Missing Brown is not new to the Bears. In 2004, he returned a fumble 95 yards against Green Bay in Week 2 before rupturing an Achilles’ tendon.

Against Arizona in Week 6 last season, he scooped up a fumble in the third quarter and returned it 3 yards for a touchdown to spark the Bears’ comeback from a 20-point deficit to a 24-23 win. While the drama was starting that night, Brown’s season would soon end. He limped off the field and was taken from the sideline on a cart after his right foot got twisted on a final running play.