Our American number one conceded it was one of those days at Upton Park as Les Ferdinand's blast went through him before he spilled the ball for Hammers crucial second goal on the 2-0 reverse.
He reflected: "It was one of those days where you do something wrong and stupid and you can't understand how it happens. You just have to look at it again.
"I don't know how many crosses I've caught this season and you think to yourself at the time 'why punch it?'
"You know you can keep control of it, help the boys out and keep possession but that was the time to punch it.
"You keep learning so you go another 100 crosses without dropping one and hope to keep those mistakes as a minimum."
Saturday's encounter was very much a goalkeeper's lot as Kasey also produced three outstanding saves, the third a contender for save of the season as he somehow clawed out Ian Pearce's header.
Kasey added: "It just makes you want to tear out what hair you have remaining and think 'whatever made you choose this job as a profession?'"
Kasey Keller held his hand up to mistakes at Upton Park and admitted: "It makes you want to tear out what hair you have remaining."