Mike Eaves and Dean Talafous each scored his second goal of the game within an 18-second span in the third period tonight, sending Team USA to a 6-2 upset over Czechoslovakia in the Canada Cup hockey tournament.

The victory improved Team USA's record to 2-2 and assured it of a berth in Friday night's semifinals along with Team Canada and the Soviets.

Earlier in the day, Guy Lafleur scored one goal and set up two others, enabling Team Canada to defeat Sweden, 4-3. In that game, Team Canada's Gilbert Perreault suffered a fractured ankle during the victory and will be sidelined for six to eight weeks. Perreault, a member of the Buffalo Sabres, was injured in the third period when he attempted to jump over sprawling linemate Wayne Gretzky, and jammed a his skate into the board.

The Perreault-Guy Lafleur-Gretzky line had contributed 25 points to Canada's offense in the first four games of the Canada Cup, with Perreault accounting for three goals and five assists. Coach Scotty Bowman said he would probably insert Boston Bruin Rick Middleton in Perreault's vacated spot.

Gretzky and Swedish winger Ulf Nilsson were also injured in the contest. The Edmonton Oiler center suffered a bruised elbow when he was slashed in the second period. Gretzky was unable to take faceoffs for the remainder of the game, but is expected to play against the Soviets Wednesday.

Nilsson suffered an injured right knee when he was checked by Philadelphia Flyer Kenny Linseman and is not expected to play for the remainder of the tournament.

In the Team USA game, Eaves and Talafous, with a goal each in the second period, brought the U.S. from a 2-0 deficit and started a surge of six straight goals. Eaves, who played but 48 games for the Minnesota North Stars last year, added two assists in the third period, giving him four points for the game.

The U.S. victory was the third major upset of the tournament and came against the team that had registered two of those surprises itself by tying the highly favored Canadians and Russians.

In the final game at Winnipeg, the Soviet Union eliminated winless Finland, 6-1, to clinch a spot in the semifinals.