Allardyce has urged his No.1 not to dwell on Rooney's strike because West Ham are now only six points from the drop zone and they need him back to his best for the relegation run-in.
The Hammers boss said: "I told him: 'Don't blame yourself son. Don't let it affect you.'
"When you let one go right through your hands and it's like a back pass, that would be more of a concern.
"I don't think it was his fault. He was in the right position. It was just one in a million. He got himself a little confused running backwards, you can see that.
"But it's because of the element of surprise. It surprised everybody in the ground. Nobody expected Wayne Rooney to shoot.
"Adrian has been outstanding. He's been there on several occasions when we've needed him."