The Maple Leafs allow five first period goals in a 63 setback to the Stars.
Kari Lehtonen made 40 saves and five Dallas players scored in the first period to send the Stars past the Maple Leafs 6-3.
Dallas took a 3-0 lead on goals by Devin Shore, Radek Faksa and Lauri Korpikoski.
After Korpikoski's goal at 11:18, Curtis McElhinney replaced Maple Leafs goalie Frederik Andersen.
Tyler Bozak scored on a power play at 13:50 of the first for Toronto, but Brett Ritchie and Jamie Benn answered to give the Stars a 5-1 lead after one.
Dallas was up 6-3 after the second. Nikita Soshnikov and Mitchell Marner scored for the Maple Leafs in the period, and Jason Spezza for Dallas.
Toronto outshot Dallas 43-20 overall.