Nichushkin made it 4-1 at 1:32 of the second period on a shorthanded breakaway, and Samuel Girard pushed the lead to 5-1 at 5:48.
Noah Gregor cut it to 5-2 at 7:44 with a backhand after he skated through the slot. Devon Toews made it 6-2 at 13:30 when he shot into an open net.
Saad scored his second of the game off a pass from Andre Burakovsky to make it 7-2 at 15:01 of the second.
"After the second it was tough, but we play them again in two days so we have to try to stay positive, send a message, because for sure we can do better," Sharks forward Tomas Hertl said. "It was not fun."
The Sharks made it 7-3 at 12:43 of the third period when Couture redirected Donato's pass in front.
"We made too many mistakes, turned the puck over and didn't give our goalies much of a chance," Couture said. "It's really the first one of those. I thought we competed harder in the third, which we can build on. When you have a game like that you have to take some positives and move on. We're going to have to be prepared against them (Thursday). Their speed is one of their best assets."
NOTES:Sharks forward Patrick Marleau played his 1,730th game, one behind Ron Francis for fourth in NHL history. … MacKinnon had six shots to extend his streak with at least one shot on goal to 227 games, tying Joe Sakic for the longest regular-season streak in Avalanche/Quebec Nordiques history. … Forward Kiefer Sherwood had an assist in 9:58 of ice time in his Avalanche debut.