The Leamington Flyers have fallen out of second-place in the Western Conference of the Greater Ontario Junior Hockey League.
Matt Murray's power play at 10:08 of the third period was the game-winner as Chatham edged the Flyers 4-3 on Sunday.
The Maroons have won four straight and six of their last seven games to jump past Leamington in the standings.
Dylan Weston, Levi Tetrault and Wyatt O'Neil scored for the Flyers who have lost three in a row.
Zach Borgiel made 29 saves for Leamington.