Left wing Craig Patrick, the Washington Capitals' leading scorer during the preseason, flew back to Washington today for treatment of his right achilles tendon, injured during Thursday night's 6-2 victory over the Toronto Maple Leafs at London, Ontario.

Patrick was in considerable pain, but the extent of the injury was undetermined.

"I was ready to take a pass from Walt McKechnie when I slipped and fell." Patrick said. "The defenseman had been getting ready to check me and he fell right on me. I don't know what position I was in when I fell, but something happened."

Patrick had produced his third goal in four games during the first period. It was the Capital's only score until a five-goal barrage in the final 20 minutes, including two shorthanded goals by Ron Lalonde, brought the Capitals their first exhibition victory.

Patrick, who worked on construction and trained diligently all summer, was in better condition than anyone on the team. He ran the fastest mile, five minutes flat, and led in pushups with 80. During the first two weeks of training camp, he had guaranteed himself a job with a superb two-way performance.

Left wing was already the most critical spot on the team. John Stewart was sent back to Hershey after a poor performance during Wednesday's 5-1 loss to New England and another free agent, Hank Nowak, did not impress Thursday.

Mark Marson, who scored the game winner against Toronto, and Ace Ralley, who netted two goals Wednesday, now are in the forefront.

Two other candidates, 1976-77 regulars Bob Sirois and Tony White, flew in tonight to join the team for Saturday's exhibition against the Detroit Red Wings.

Newspaper advertisements here proclaimed all tickets at $6 to see "Ted Lindsay's Aggressive Red Wings" and the Capitals. The strong-arm approach helped Detroit lose its first four exhibitions going into tonight's contests as the opposition poured in power-play goals.

Detroit's roster includes such noted bad men as Dan Maloney, Dennis Polonich, Steve Durbano, Jerry Rollins (all time Western Canada League penalty king), Len Ircadia (International League penalty champ) and Dave Hanson, who played "Killer" in the movie "Slap Shot."

While the Red Wings punched their bags or walls or whatever, the Capitals bused over today from London, with the principal stir created by Hartland Monahan's dropping a rubber snake on the shoulder of Bryan Watson, who has a phobia about those things.