Cal Petersen made 35 saves, improving to 3-0-1 in his last four starts.
Oskar Sundqvist scored late in the third for the Blues, who fell to 1-5-1 in their last seven home games.
The Kings made it 2-0 at 16:08 when Athanasiou scored on a wrist shot, beating Binnington to his glove side.
Binnington made his fifth consecutive start and sixth in the team’s last seven games. He stopped 19 shots in falling to 8-6-2.
St. Louis was unable to score with a 6-on-5 skating advantage for 3:25 on a delayed penalty in the third. Sundqvist scored on the ensuing power play at 18:14.
St. Louis D Carl Gunnarsson will miss the rest of the season with a right knee injury. He is the fifth Blues player on injured reserve. Gunnarsson got hurt Monday in a puck battle with Kings forward Gabriel Vilardi along the boards behind the net. … Ivan Barbashev had surgery on his left ankle and will be re-evaluated in six weeks. … The Blues remain without F Jaden Schwartz (lower body) and D Colton Parayko (back). This was the sixth game Schwartz has missed and the fourth for Parayko. … Kings forward Jaret Anderson-Dolan (upper body) was placed on injured reserve, retroactive to Feb. 18. … Kings D Mikey Anderson was a late scratch due to a lower-body injury.
Blues D Steve Santini was assigned to the taxi squad. … Kings D Austin Strand was recalled from the taxi squad.
Blues C Tyler Bozak, who hasn’t played since taking a big hit from Mark Stone on Jan. 26, did not skate Wednesday morning. After skating the past two days, Bozak is “not feeling ready yet,” according to coach Craig Berube. … RW Vladimir Tarasenko (shoulder) was on the ice for the fifth consecutive day at the morning skate. Taraskenko is recovering from surgery he had five months ago on his left shoulder, his third operation on the shoulder and second since Oct. 27, 2019.
The Kings play Friday night at Minnesota.
The Blues play Saturday night at San Jose.