Celtic keeper Artur Boruc insists fans deserved better after Tony Mowbray's side were upset 2-1 by Hapoel Tel Aviv in Europa League action.
Georgios Samaras' 25th minute opener put the visitors in front for much of the game, but late goals from Nemanja Vucicevic and Maaran Lala turned the match around.
Boruc does not believe Celtic should have lost the game and insists their second-half display was unacceptable.
However, the Poland international is not dwelling on the surprise loss and says there is still plenty of time left to qualify from Group C.
"I feel sorry for the supporters," said Boruc. "They have travelled to the end of the world to support the team and watch the game.
"I do feel sorry for them because the performance was bad. The second half was really, really bad.
"I made some good saves, but it wasn't enough. Celtic shouldn't be beaten in Israel. But it's only the first game.
"There is a long way to go and we can still go through. There's a big chance for us and we'll see what happens in the next few games."
Group favourites Hamburg were beaten 3-0 by Rapid Vienna and Boruc now hopes the Bhoys can get their Europa League campaign up and running against the Austrians.
"Rapid beating Hamburg 3-0 was a surprise," he said. "But we play them at home in the next game and that's better for us.
"I think we'd need to win the three games at home and see if we can do anything in the two away matches."
Meanwhile, Samaras is keen to ascertain the severity of the leg injury he suffered after slipping in the technical area while attempting to keep the ball in play.
Although the Greece international has been told nothing is broken, he remains in a lot of pain and is a doubt to feature for Celtic in their SPL clash against Hearts on Sunday.
"I really don't know how bad it is but it is very sore," said the former Manchester City man.
"I don't even know what happened. All I know is that I couldn't stop myself and slipped on the concrete.
"Normally around the pitch there's no such surface - it is dangerous and that should not be allowed.
"I've been told nothing is broken. But right now I'm in a lot of pain with both my shin and my ankle and until I am examined in Glasgow I can't say any more."