Celtic manager Ronny Deila lamented his side's failure to add more goals in their 2-0 UEFA Champions League qualifying win over Stjarnan.
First-half goals to Dedryck Boyata and Stefan Johansen were enough to give Celtic a buffer heading to the second leg in Iceland on Wednesday, but Deila remained sceptical it was enough to see them advance.
Celtic are playing Icelandic opposition in the second qualifying round of Europe's top club competition for the second straight season, the Scottish powerhouse thrashing KR Reykjavik 5-0 on aggregate in 2014-15 after a 4-0 home-leg win.
Deila rued Leigh Griffiths' missed penalty late in the match - one of many chances that went begging for the hosts.
"Two-nil is a good result but I hoped we could finish them off. We had chances to win more but we were not effective enough," Deila said, according to Celtic's official website.
"In the end, I'm a little bit disappointed that we didn't score more. But it's good we have a clean sheet and two goals to go on.
"We will have a good preparation for next Wednesday and we have a very good chance to make the next stage.
"We deserved to win but we could also have scored more. They also had one or two chances and it was good they didn't score. I'm happy but I'm not too excited.
"There were a lot of things we are used to. They played very deep, with 10 men, 40 yards from their goal. But that's football, some teams need to do that and it was hard for us."
Former Manchester City defender Boyata and ex-Dundee United forward Nadir Ciftci both made their debuts for Celtic, much to Deila's pleasure.
"Both of them showed they have something to give us," Deila added.
"Boyata played very well and scored a goal. I'm very satisfied with him.
"Nadir of course needs time. He has only trained one-and-a-half weeks as he started later with Dundee United and he has only been with us since last Thursday.
"Nadir was good until he got tired. He needs some playing time and training to get to the level where he needs to be."
