Kirkland said: "All the lads are down, of course, but we just have to keep going and to keep believing in ourselves.
"If we'd scored from half of our chances at Sunderland then we would have won the game comfortably. Their goalkeeper had a fantastic game, just as he did at Anfield a few weeks ago.
"Things are not going our way at the moment but we are confident our luck will turn. I thought we played some good football at Sunderland and definitely didn't deserve to lose."