The Red Wings were shut out 4-0 by the Maple Leafs at Joe Louis Arena in the team's last action before this weekend's All-Star Game.
Auston Matthews scored early in the first period and Frederik Andersen made 22 saves for his third shutout of the season.
Roman Polak scored late in the second period and James van Riemsdyk and Nikita Soshnikov had goals in the third to give Toronto a comfortable cushion.
The Leafs moved a point ahead of Boston in the Atlantic standings and into third place for the division's third guaranteed spot in the playoffs.
Petr Mrazek stopped 24 shots for the Red Wings.
The Wings are off until Tuesday when the host the New Jersey Devils.