The Canaries are fighting for their lives in the Premier League, but they gave up three goals and fell to a heavy away defeat.
It means they are still bottom of the table and running out of time to mount a battle to survive.
Farke acknowledged the poor performance after the game, with his side now seven points from safety with 11 games to go.
"This was a missed opportunity for us," he told reporters.
"We started quite well, we were on the front foot and created chances but I was not happy with our physicality in the final third. When you are that dominant and create so many opportunities we need to do better. But we lost too many offensive duels in both boxes.
"We had six against two in our box and they were able to score. Both directions we lacked that sharpness and physical edge.
"Second goal, same topic, the second phase of the set piece they had two or three players greedy to score and we were not switched on to protect our own goal.
"This is crucial. I can't accuse my lads' attitude, our philosophy, but you have to be ready to win the crucial duels in both boxes.
"Third goal, unnecessary loss of ball, too soft, and we still had chances to regain possession.
"Perhaps in our back four it is not easy when you go from a solid defence to two injury changes.
"We had to bring in Ben Godfrey and Jamal Lewis who were not in their rhythm. We had no choice because of injuries.
"I am not accusing those boys. I was more annoyed with our lack of physicality."