With Wayne Gretzky's participation still uncertain, organizers yesterday announced a preliminary 37-man roster for the Canadian team for this year's Canada Cup that includes three members of the Washington Capitals -- defensemen Scott Stevens and Larry Murphy and forward Mike Gartner.

Gretzky, the Edmonton Oilers' star, is expected to decide next week whether he will participate in the international tournament that will begin in late August. "We're pretty sure he's going to play," Montreal General Manager Serge Savard said. "He just wants a few weeks of rest."

The preliminary roster for the Canada Cup squad, which will report to training camp Aug. 3, was selected by Savard, Philadelphia's Bobby Clarke, Edmonton's Glen Sather and the New York Rangers' Phil Esposito.

The list of players will be trimmed during camp. The final team will consist of three goalkeepers and 20 skaters. Canada will face the United States, Soviet Union, Sweden, Czechoslovakia and Finland in the round-robin competition starting Aug. 28. The two-of-three final series will take place Sept. 11-15 . . .

The National Hockey League suspended Philadelphia Flyers goaltender Ron Hextall for the first eight games of next season as a result of a stick-swinging incident in the fourth game of the Stanley Cup finals against Edmonton on May 24.

Brian O'Neill, the league's executive vice president, announced the suspension. Hextall, the most valuable player in the finals despite Philadelphia's four-games-to-three loss to the Oilers, received a major penalty for slashing forward Kent Nilsson. f bone spurs from the ankle, grafting of bones in the