After fighting back from 2-0 down to level the game, Defoe had a golden chance to put the North Londoners in front in the final minute of normal time.
"We should have won," Defoe told The Mirror. "If I am honest I felt throughout the game we were the better side. I played up front on my own and they had five in midfield. I scored, Gareth [Bale] scored and it was 2-2. Then we had that chance.
"Gareth played it across the box so that I could just tap it in, but I stretched and missed it. I was convinced that if I'd got to it I'd have got it in. After that, they got the penalty and scored to win the game.
"Looking back, I think maybe we were not meant to win on that day. It was all a bit mad. I thought about that miss afterwards for ages."
Spurs return to the Etihad Stadium on Sunday.