Kris Versteeg, Colby Armstrong and Phil Kessel added goals for the Maple Leafs, who scored nine straight -- including six in the second period -- for their second straight win overall and third consecutive on the road.
"For them, it was like quicksand," said MacArthur, who played 21 games for Atlanta last season. "The harder they tried the worse it got."
James Reimer made 41 saves for the Maple Leafs, who had six goals in a span of 7:43 of the second period. Toronto had a 2-1 lead before the offensive barrage started with Armstrong's goal at 12:06.
"That was one of the best second periods I've ever seen," Reimer said. "I'm not sure how it happened."
Tobias Enstrom gave the Thrashers a 1-0 lead early in the first period before Atlanta's defense collapsed.
Ben Eager didn't help matters. The defenseman's four penalty minutes for roughing and cross-checking led to a power-play goal by Grabovski, his 16th overall this season, that gave Toronto a 2-1 lead.
Late in the second period, Eager was ejected and given a match penalty for intent to injure Armstrong, a former Thrashers forward. That led to a power-play goal by Kulemin, two by MacArthur, and another by Kessel.
Eager appeared to retaliate for Armstrong's hit on Bryan Little a few seconds earlier, but he might have been trying to avenge Armstrong's clean hit against Rich Peverley's knee in the first.
"We don't condone anything," Thrashers coach Craig Ramsay said of Eager's performance. "We want our players to play hard. We want them to play physical with body checks and fight for the puck. We can't condone that."
Grabovski's 17th goal made it 5-1 at 15:15 of the second. He has scored 12 times in 14 games and has recorded a point in five of six.
"Once it got to 5-1, things kind of got away on the penalty kill," Thrashers defenseman Ron Hainsey said. "We weren't able to do the job, and that's disappointing because our PK has been really good for the better part of two months."
Toronto was trying for its first 10-goal game since Jan. 4, 2007, when the Maple Leafs won 10-2 at Boston. The Maple Leafs have scored at least 10 goals 35 times.
Versteeg started the onslaught when his 12th goal, a wrister from the right circle, lifted Toronto into a 1-1 tie 9:43 in.
Thrashers goalie Ondrej Pavelec played into the second before being replaced by Chris Mason, who was pulled later in the period. Mason played the entire third period and finished with six saves on 10 shots.
"That was unbelievable," MacArthur said after of Atlanta's three goalie changes. "I feel bad for their goalies. I don't know if some of the shots were screened or not."
Pavelec (15-9-4), began the game ranked second in the NHL in save percentage, but he had a rough night -- stopping 19 of 24 shots.
"We were embarrassed, but there's another day," Pavelec said. "We gave it to them. We paid a price. Everything went wrong."
Toronto D Tomas Kaberle had four assists. ... The Maple Leafs improved to 13-5-2 at Philips Arena. ... Atlanta LW Evander Kane missed the game because of a lower body injury.
Copyright by STATS LLC and The Associated Press
Arena: Philips Arena Location: Atlanta, Georgia
Referees: Frederick L'Ecuyer, Kelly Sutherland Linesmen: Scott Cherrey, Dan Schachte
Attendance: 14,592 (78.7% full)
Team Stat Comparison
Power Play Goals
Power Play Opportunities
Shots on Goal
Tobias Enstrom (8)
Assist: Ben Eager
Kris Versteeg (12)
Assists: Colby Armstrong, Carl Gunnarsson
Mikhail Grabovski (16)
(Power Play) Assists: Phil Kessel, Tomas Kaberle
Nikolai Kulemin (14)
Assists: Mikhail Grabovski, Mike Komisarek
Mikhail Grabovski (17)
Assists: Clarke MacArthur, Nikolai Kulemin
Nikolai Kulemin (15)
(Power Play) Assist: Tomas Kaberle
Clarke MacArthur (11)
(Power Play) Assists: Nikolai Kulemin, Tomas Kaberle
Clarke MacArthur (12)
(Power Play) Assists: Kris Versteeg, Tomas Kaberle
Phil Kessel (17)
(Power Play) Assists: Francois Beauchemin, Tyler Bozak
Patrice Cormier (1)
Andrew Ladd (14)
Assists: Bryan Little, Niclas Bergfors
From Elias: From Elias: The Maple Leafs scored 4 power-play goals over the course of 3:32 between the 2nd and 3rd periods on Friday. The last team with 4 PPG in under five minutes of game action was the Florida Panthers on Dec. 9, 1998 vs the Ottawa Senators (4 goals in 3:51).
The last team to do so in a shorter time span than the Leafs tonight was the Hartford Whalers against the Pittsburgh Penguins on Feb. 26, 1989 (4 goals in 2:28).