Samuel Girard one-timed a pass in the high slot from MacKinnon to make it 3-1 at 19:58. McKinnon missed eight games with a lower-body injury. Kadri brought the Avalanche to within 3-2 with a backhand from the slot to make it 3-2 at 11:57 of the second period.
Travis Dermott gave Toronto a 4-2 lead at 12:44 with his first of the season. Tavares jammed a rebound at 16:28 to make it 5-2.
Matthews took a pass from Marner in the slot for a 6-2 lead 44 seconds into the third period. He completed the hat trick at 8:41 when he shot from the left face-off dot to make it 7-2. He has scored six goals during his goal streak and has scored 13 this season.
"Just Auston being Auston," Campbell said. "Just spectacular, and he does it at both sides of the rink. It's great to see him get rewarded with three goals tonight. They've got a lot of great players over there, but as soon as they scored we kind of put our foot on the gas and did not give them much life."
Engvall made it 8-2 at 10:08.
Kadri deflected a shot at 16:36 to make it 8-3. The forward, who played his first 10 NHL seasons for the Maple Leafs, played his 687th NHL game.
"We just didn't play good enough tonight," Avalanche captain Gabriel Landeskog said. "When you get in a hole like that, it's tough. We'll come back strong tomorrow (at the Montreal Canadiens)."
Jett Alexander, a goalie with the University of Toronto, was the emergency backup for the Avalanche in the first period. Justus Annunen, who was recalled from Colorado of the American Hockey League, took over as the backup to start the second period after arriving at the arena.
Goalie Michael Hutchinson, who was recalled from Toronto of the AHL late in the afternoon, backed up Campbell because Joseph Woll was unavailable due to stiffness after practice Tuesday.
NOTES: Kadri scored 161 goals in 561 games for the Maple Leafs. He has scored 39 in 126 games for the Avalanche. He was traded prior to the 2019-20 season. ... The Avalanche played their 1,000th regular-season road game since relocating from the Quebec Nordiques for the 1995-96 season. ... It was the first time Toronto scored eight in a game since Dec. 23, 2019 when it defeated the Carolina Hurricanes 8-6. ... Bunting extended his point streak to five games (two goals, five assists), which ties Moritz Seider of the Detroit Red Wings for the longest by a rookie this season.