Kings coach Darryl Sutter confirmed Tuesday morning that Richards remains sidelined and won't dress for Game 3 against the Chicago Blackhawks.
Richards did not partake in the morning skate, which was a clear indicator he was out.
"Yes, absolutely [Richards is out]," Sutter said. "He's done a little bit every day but it's the same, no progress."
Richards took pregame warm-ups Sunday night but was pulled out of the lineup just prior to Game 2. The Kings' leading scorer in the playoffs, Richards was rocked by a big hit from Chicago's Dave Bolland near the end of Game 1.
"If it was just about Mike Richards making the decision, Mike Richards is playing tonight," Sutter said. "You got guys who want to play, you got guys who don't want to play. Mike Richards wants to play."
Tyler Toffoli replaced Richards in Game 2 and is expected to do so again Tuesday in Game 3.
ESPNLosAngeles.com's Arash Markazi contributed to this report.