Buchnevich scored a natural hat trick, Thomas had three assists and Binnington made 20 of his 38 saves in the second period for the Blues (30-24-2), who had lost two in a row and three of their past four. Binnington’s shutout was his third of the season and 15th in the NHL.
"'Binner' was outstanding," St. Louis coach Drew Bannister said. "We made it way more difficult on him and ourselves than it needed to be. He played outstanding."
Varlamov made 21 saves for the Islanders (23-19-14), who have lost four of their past five (1-2-2).
"It's all about puck management," New York coach Patrick Roy said. "The PK, we just need to clear and all of a sudden, you give up a goal and you win the face-off at center ice and then again, you don't manage that puck well and the line is very, very, very thin.
"It's a fine line between making plays and not making plays. And obviously I thought we tried to battle back in that game and their goalie was really good. I mean, it's hard to play catch-up hockey in situation like this."