"I thought we were too submissive and didn't get on the ball enough or in their faces," McDermott told BBC Sport. "I made some changes and we were much better in the second half. We came up against a very good side today and they deserved the win.
"We've got to move on very, very quickly. Today was a learning curve for all of us. Spurs is a team full of world-class performers, but we didn't cause enough problems for them, especially in the first half."
Reading have the chance to pick up their first win of the campaign on Saturday when they travel to West Bromwich Albion.