He said there was a collective disappointment in the Sharks dressing room.
"That wasn't us," he said. "We talked about it today. We watched some tape. That's flushed now."
Kane's suspension won't impact center Joe Thornton's status for Game 2. Thornton, who has been out since Jan. 23 recovering from knee surgery, continues to progress but won't be in the lineup.
"Joe is coming along well," DeBoer said. "Every day he's getting a little bit better. He's looking a little bit better on the ice. He's not going to play next game."
Said Thornton: "Nothing's changed. Eventually it just has to get a little bit stronger. Day to day, still. … The good thing is that it's getting better.
"The boys have had good bounce-back ability all year now. … I've been sitting on the sideline for a while now. Obviously, you want to help out the fellas, but they're doing a great job, having a great playoffs, so not worried about them at all."
The Sharks had issues with the speed of the Golden Knights, a significant contrast from the first round against the slower Ducks.
"Yes, they're a fast team, but we've played fast teams and we've had success against fast teams," DeBoer said. "We didn't do what we needed to do. We didn't manage the puck properly. … Beyond that, we didn't win enough battles when you take out the X's and O's of the game. They were the hungrier team."
The result was the Sharks' worst playoff loss since May 11, 1995, when the Calgary Flames defeated them 9-2 in Game 3 of the Western Conference Quarterfinals.
"We played as poorly as we've played last night, before," DeBoer said. "It's not the worst game in the history of the San Jose Sharks. It might be on the scoreboard in playoff history. I don't think it's the worst game we've played in the history of hockey.
"It got away from us. They got seven goals. We didn't get any. It was ugly. We've played poorly before. We'll get it back."