Kayal said: "Before the game, we knew we'd have to work hard in defence and that most of the time we wouldn't have the ball.
"But the goal was with the last cross and we couldn't get the ball away. True, we were playing the best team in the world, but we're professionals and more than anything we wanted to come away with a good result.
"It's a shame because we could have held on to the ball for that last minute."
Barcelona manager Tito Vilanova believes his side deserved the win.