Dean Richards was judged to have up-ended Thierry Henry and, with the Frenchman off the pitch following treatment, spot-kick duty fell to Lauren who trickled his effort into the net with Kasey astounded having already moved.
With Teddy having levelled the match minutes before the outcome was a huge disappointment to the team after a much improved second half showing.
"Definitely," said Kasey afterwards. "We came out in the second half, looked a lot better and got the goal late.
"Unfortunately, I didn't see the incident, I'd have to see it again, I just saw a bunch of people and Chris Perry clearing it. Then the referee blew for a penalty.
"Like I say, I'll have to see it again. We were very disappointed in the changing room.
"We were disappointed with ourselves in the first half, we didn't play the type of football we're capable of. We came out in the second half and did exactly that and got the goal - we just couldn't hold on.
"It's just a shame, a real shame. Everybody's disappointed after getting back into the game and then losing like that."
Kasey says the title race is not done and dusted, but insists teams like Arsenal and Manchester United have set a standard we should strive to attain.
"We want to be competing with this team. They are setting the standard right now along with Manchester United - showing what it takes to get up there.
"In the second half we were right up there with them. Obviously we need to take that step further and be in a position where we can come here and win.
"There's a few games left and we'll see what happens. We had our chance and unfortunately came up a little short."
Kasey Keller expressed the team's disappointment at Arsenal's late winner on Saturday and confessed that he did not see the incident that led to the penalty.