(AP) -- Next week's big "Monday Night Football" showcase could feature a quarterback matchup of Jason Campbell of the Bears vs. Colin Kaepernick of the 49ers">49ers. Not exactly the creme de la creme of the NFC.

Why? Concussions, of course.

With so much attention paid to replacement refs and bounty ruling appeals this season, it's an issue that's slipped a bit under the radar lately. But it's hard to ignore this: 25 percent of Sunday's NFL games saw a starting QB leave with a concussion.

Two were Chicago's Jay Cutler and San Francisco's Alex Smith, whose teams play each other next Monday. Both stayed in Sunday's games for several plays after what appeared to be head-rattling hits. Smith even threw a TD pass while playing with blurred vision before he departed, according to coach Jim Harbaugh.

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