Butch Goring of the New York Islanders summed up his team's 5-1 loss to Boston Thursday night in a single sentence: "They showed a lot of spunk out there and we didn't capitalize on the chances we had."

Clearly disappointed at having to play yet another semifinal game here Saturday night instead of preparing for a final-round meeting with Edmonton, the Islanders skated through a brief practice today, vowing not to return to Boston for a seventh game on Sunday. New York leads the series, 3-2.

"Maybe we expected them to lie down," said Denis Potvin. "We didn't stick the knife in." He indicated that situation would change Saturday night.

"We'll have to come out skating and shooting early," said Bob Bourne. "A quick one- or two-goal lead."

In Boston Thursday, the Islanders got that edge after Bob Nystrom scored a little over three minutes into the game. But the Bruins' checking, and a solid, workmanlike effort by goalie Pete Peeters changed everything.

"A few of our key guys just weren't in the game tonight," admitted Islanders Coach Al Arbour. "But you've got to give them (the Bruins) credit. They worked hard, throwing everything at us. We struggled in our end."

Mike Bossy seemed to spend every moment on the ice struggling. After a hat trick in Tuesday's game, Bossy was held without a point for the first time in this series. Luc Dufour shadowed Bossy's every move, and Bossy was limited to a single shot on goal.

His line (with Clark Gillies and Bryan Trottier) accounted for just two shots on Peeters, while the Bruins outshot New York, 45-22.

"As much as we needed to take advantage of our scoring opportunities, it was more important that we get into our checking game," said Bruins Coach Gerry Cheevers. "And I think we checked better than we ever have before in this series."

Indeed, Boston's nonstop checking scarcely gave the Islanders enough space to skate or pass.

"The thought of being eliminated . . . we were really thinking about that," said Craig MacTavish. "And that thought helped us come up big."

Peeters, whose earlier performances in New York yielded 15 goals in two games, came back with the form he had shown all season long, shutting down the Islanders for the last 56 minutes of the game.

"Pete's the kind of guy who will come up with the big effort," said defenseman Brad Park. "And if you minimize their chances, give them five instead of 10 shots, Pete will stop most of them."

Of course, Peeters will be in the nets for the Bruins Saturday night, as he has been for all 15 of their playoff games. Billy Smith started Thursday night for New York, but was replaced for the third period by Rollie Melanson. However, Melanson brushed aside suggestions that he might start on Saturday.

"Al (Arbour) only did that to get Smitty some rest," he said. "I'm sure you'll see him out there tomorrow."

Should Boston win the series, the Bruins would become only the third team (others are the 1975 Islanders and the 1942 Toronto Maple Leafs) to overcome a 3-1 deficit . . . Islanders defenseman Ken Morrow, who underwent arthroscopic surgery on his right knee Wednesday, is listed as "questionable" Saturday.