Celtic boss Tony Mowbray admitted to disappointment at only drawing 1-1 with Rapid Vienna in Europa League Group C.
"My emotion is frustration," Mowbray said. "We did enough to get three points but didn't score that second goal. We pushed hard but it didn't come. You've got to give them credit for defending well.
"The big frustration is giving them the early goal, knowing the way they play on the counter-attack.
"It was a very evident individual error. That's football, players make mistakes and you get on with it."
"It is a concern and we have talked about it, that we have not converted enough chances," he said.
"We also have an unfortunate habit of conceding goals in the first five minutes in three home games on the bounce. Concentration is one of the things we talked about.
"But I take the positives from football. I know if we play as well as we did tonight for long spells, we'll be fine."
Mowbray also remained upbeat about Celtic's qualification hopes.
"I think there's enough evidence from tonight's game that we can go to Vienna and give them problems and I know we can give Hapoel problems," he said.