Kopitar made it 5-1 with a power-play goal at 11:24, scoring from in front after Kempe's cross-ice pass pinballed to him off Brett Howden and Alex Pietrangelo.
Gavrikov cut it to 5-2 at 14:10 with a short-handed breakaway goal.
"In moments or situations of the game, there were some good things, some execution in certain situations," McLellan said. "You certainly look for the positives. Tonight's disappointing because we weren't engaged. We'll look for positives. [Special teams] were two of them."
NOTES: Eichel, who played his 100th game with the Golden Knights, has 11 points (one goal, 10 assists) during an eight-game point streak. … Brossoit is 5-0-3 with a 2.44 goals-against average and .921 save percentage in nine games (eight starts) this season.