"Because we never used the ball well enough, we were unable to test their substitute keeper.
"I took Martin Rowlands off because he had been booked after the challenge on their keeper and I didn't want to risk him being sent off.
"Swansea are a very good side and Roberto Martinez has done very well for a very passionate crowd, but at the end of the day we have come away from a difficult place with a point."
Swansea boss Roberto Martinez said "When you lose your keeper you have to squeeze the player further up the field and that is exactly what we did.
"There are many positives to be taken from this game as we created enough chances."
After De Vries was carried off the field, he was taken to hospital during the half-time interval.
"He has a suspected broken jaw and cheekbone and will have surgery in the next day or so," said Martinez.
"I don't think their player is malicious, but I do believe that he could have avoided contact with my goalkeeper's face.
"I was very pleased with the attitude of all my players and proud of their reaction following the injury."