The boys were in the lead, in command and desperately unlucky not to be three goals to the good when the French striker stretched his legs in pursuit of a ball to the edge of the Spurs penalty area.
Kasey considered the ball was there to be collected and made a dash from his line but, sadly, was second to the ball.
"We played tremendously well, got the goal early, could have scored two or three more, but then, just before half-time, I made the mistake of under-estimating the pace of Thierry Henry," reflected Kasey after the game.
"I won't be the last one to do that. He beat me to a ball that I thought, until the very last second, was mine all the way. He played for it and was smarter than me on that occasion."
Only a matter of minutes before, Kasey reacted smartly to divert a Henry header around the post after being largely inactive during the first half. He doesn't feel that the adrenalin generated by the save was a factor in his later decision making.
"There was that but that's the way I play. I'm out trying to help the guys out and, as I said, there are times you know when you take off that you are not going to get there but you've already committed yourself.
"This was one time I didn't even think twice that I was going to get there - but I under-estimated the pace of the fastest player in the league and that's something you can't do."
Kasey Keller conceded that he under-estimated the pace of Thierry Henry in the passage of play that led to Arsenal being awarded a penalty to level the scores on Sunday.