It was the 22nd career shutout and third this season for Mason, who stopped 33 shots in a 5-0 win against Detroit last Tuesday after getting pulled by coach Craig Berube in two of his previous three starts. Mason got a break with less than 3? minutes left, when Justin Williams tried a wraparound and hit the left post.
Claude Giroux added his 17th goal on a power play with 1:58 left, converting a cross-ice pass at the left of the crease from Scott Hartnell while Matt Greene was serving an interference penalty.
The Flyers have scored a power-play goal in six straight games.
The Kings have scored fewer than three goals in 16 of 20 games since their 25-8-4 start, and are 5-13-2 during that stretch with five shutout losses. They have only three goals in their past six games combined, all of them by Anze Kopitar.
The Flyers had managed only five shots on net before Simmonds got his 18th goal at 7:48 of the first period. Jonathan Quick, who faced only 13 shots, overplayed Vincent Lecavalier at the right of the crease along with Kings defenseman Jake Muzzin following a turnover by the Kings in their zone, and Simmonds slammed the puck into a wide-open net.
The Kings' Robyn Regehr played in his 1,000th NHL regular-season game, becoming the 98th defenseman in NHL history to reach that plateau, and the club marked the occasion with a pregame ceremony. Regehr's first game was Oct. 28, 1999, with the Calgary Flames at Ottawa. Among those taking part in Saturday's ceremony were former Calgary teammate Craig Conroy and Regehr's grandmother, who wore a Flames jersey with his old No. 28.
It was the first meeting between the Kings and Flyers since Oct. 15, 2011, when Los Angeles won 3-2.
Saturday also was a reunion for Kings center Jeff Carter, whom the Flyers traded to Columbus on June 23, 2011 - the same day they dealt Richards to Los Angeles. Eight months later, the Kings acquired Richards by sending Jack Johnson to the Blue Jackets. Carter and Richards led Los Angeles to its first Stanley Cup title in 2012, two years after helping the Flyers get to the finals.
NOTES: Richards has one goal in his past 32 games, and that one came on the power play. Carter has no goals in his past six games, following a four-game goal streak. ... Kings C Colin Fraser is one of seven forwards in the league to have played 30 or more games this season without scoring a goal - and average at least nine minutes of ice time. ... The Kings are 19-3-0 when scoring more than two goals. ... Among the numerous Kings-Flyers connections is fan favorite Ian Laperriere, who played eight-plus seasons with Los Angeles and is now an assistant coach with Philadelphia.