The Dutch international admitted that Stoke's 88th minute equaliser yesterday was a bitter blow and left him feeling like the game had been lost.
"It feels like a defeat. We didn't play our best football but we were fighting for the right result and to concede in the last minute and then miss that chance at the end is unbelievable," he said.
"We are angry we gave a goal away and didn't win the game. We are really disappointed.
"Confidence is not very high at the moment but we have to keep going, work really, really hard and come out of this as soon as possible."