"He didn't skate today, so he won't play tonight," Kings head coach Darryl Sutter said Thursday morning as his team prepared for Game 4 at Staples Center.
Richards skated for the first time Wednesday with the scratches at the team's practice facility, but obviously didn't feel well enough Thursday morning to take another crack at it.
"The protocol is very clear, you've covered enough concussions surely, you know the protocol," Sutter said to a reporter during the media briefing.
Richards was felled by a big hit from Chicago's Dave Bolland late in Game 1. He hadn't missed a game all year until this series.
Tyler Toffoli replaced Richards in the last two games and did so again in Game 4. Toffoli has a goal and two assists while filling in for Richards.
The Blackhawks own a 2-1 lead in the best-of-seven series.