Ronny Deila blasted his players after an argument during Celtic's UEFA Champions League qualifying tie with Stjarnan.
Celtic manager Ronny Delia blasted his players' "unprofessional" behaviour after they squabbled over who should take a penalty in the 2-0 win over Stjarnan.
Goals by Dedryck Boyata and Stefan Johansen gave Celtic a healthy lead in the Champions League second qualifying round tie, but Johansen was seen arguing with Leigh Griffiths over who should take a late penalty.
Griffiths eventually took the spot kick, only to see it saved, and Deila was less than impressed by the apparent disharmony amongst his players.
"It's very clear who's going to take that penalty; the guy who took the penalty," Deila told BBC Radio Scotland.
"Leigh has taken penalties before so that is quite clear. We can't have it like that, it's unprofessional."
Despite making his disappointment at the incident very clear, Deila remains confident his side can progress in the competition when they travel to Iceland for the second leg in Iceland on Wednesday.
"We created a lot of chances, we should've scored more goals but 2-0 is a good result and that should be enough when we get up to Iceland," he said.
"We had five big chances in the first half, we should have at least one more goal there. I think we had opportunities to kill the game but that's football. I'm very happy that we didn't concede anything."