"We are really disappointed, particularly after the good start we made to the game," said the defender.
"We scored a good goal and we were controlling the game but after they drew level we started to lose control of the game.
"Dirk [Kuyt] had a good chance when he went one on one but unfortunately he was not able to score and I think if that had gone in it might have changed the game.
"But you have to give credit to Chelsea because they played really well, especially in the second half, and they were more effective.
"After going behind we probably became a little bit desperate to score a goal to give ourselves a better chance for the second leg. We started to give the ball away easily and this meant they could use counter attacks which is one of their strengths.
"We know that it will be really difficult for us now because as last night showed we are playing against a really good team but we will not give up.
"We will fight until the very end because this season has shown that there have been many occasions when we have had setbacks but we have managed to turn things around.
"This means that we have to fight until the very end.
"We know it will be difficult but we want it really badly and we will try everything."