In the summer of 1972, McKenzie was disgruntled at being left unprotected in the expansion draft, and he signed as player-coach with the Philadelphia Blazers of the newly formed World Hockey Association (WHA). In thirteen games he recorded only two wins and eleven losses, and he stepped down as coach in favor of veteran Phil Watson. He continued to play effectively for the Blazers, then for the Minnesota Fighting Saints, the Cincinnati Stingers and finally the New England Whalers. He finished his career in the WHA's final season in 1978-79, having played twenty-one seasons of professional hockey in the NHL and WHA.