The Black Cats took the lead through Adam Johnson in the 36th minute at the Stadium of Light, but conceded twice to suffer a 2-1 loss.
"Very disappointed, for many reasons: one, because we don't have the heart to compete with Tottenham for long periods," he told Sky Sports News. "To go ahead and score with a great goal, the type of goal we try to convince the players that they can do, but then something happened.
"Something can happen in the last minute, a simple foul, but the ball is played in and it drops and they are better than us, they are quicker than us. And once more an own goal, I don't know what to say about that. I have never seen it before.
"And then it was too open, you cannot play that way against Tottenham. You shouldn't be in that situation again."
Sunderland are currently at the foot of the league table with eight points from 15 matches.