The Sixers lost 102-94 to the Central Division side, leaving them on a 22-game losing streak.
The coach told reporters: "Winnable game. I say that because a group that's been losing, still stays together.
"They still compete. I'm proud of them. There is just no inch for error. There's no wiggle room at all."
The Sixers will have another chance to end their losing run when they host the New York Knicks tomorrow.