Defoe's stunning volley proved the only goal of the game at the Stadium of Light as Sunderland recorded a fifth consecutive victory over their North East rivals.
Krul was spotted chatting with Defoe in the tunnel at half-time but the Netherlands international maintained it was not a sign that he did not care about the loss.
"I think it was an unbelievable goal," Krul told Sky Sports.
"What I actually told him I probably can't repeat on television because it wasn't just a nice gesture.
"It was a fantastic goal, you have to accept that. What I actually told him was more in the region of what a lucky guy he is with a bit more venom behind it.
"I've been here 10 years at this club and I'm as hurt as anyone. It's not justified.
"I'm a Geordie, I've been here 10 years and I'm going home with a lot of pain in my heart, to see those fans having to travel back without a win again hurts me as much as them.
"That has to come across."
