Celtic manager Neil Lennon thinks fans' criticism of striker Georgios Samaras is unfair, but admits there is a need for greater quality in attack.
The SPL club were held to a frustrating goalless draw against Sion in the first leg of their Europa League play-off at Parkhead on Thursday night.
Fans booed when Anthony Stokes and not Samaras was replaced by Shaun Maloney in the second half and then cheered when the Greece international's number was held up to allow Paddy McCourt to come on with minutes remaining.
Asked if he understood their response to Samaras, the Celtic boss said: "I understand the frustration at times, but he brings a lot to the team.
"He did a good job at set-pieces. He missed some decent chances and he knows himself that he can play better. But I think he gets a lot of criticism that is sometimes unwarranted."
Lennon is still confident of progressing through to the group stages, as he said: "I feel we have enough in the team to score goal. I was delighted with the clean sheet and the tie is far from over.
"But it was disappointing. We had enough chances in the second half to win it. We needed better quality in the final third."
Celtic found Sion goalkeeper Andris Vanins just too formidable a barrier, as he made good saves from Charlie Mulgrew, Kris Commons and substitute Maloney.
But Celtic's Swedish defender, Daniel Majstorovic, believes it is still possible to progress on aggregate.
The Hoops were knocked out of the UEFA Champions League and the Europa League at the qualifying stages last season and could face a similar fate if they do not improve in Switzerland.
However, Majstorovic said: "I'm not thinking about waiting another year to play in Europe. Now we have the chance and we need to take it.
"They will be a different team at home, but with the quality we have we have nothing to fear."
Lennon is hoping to have Gary Hooper, Beram Kayal and Kelvin Wilson back for the return game after all three missed out with injury.
"Wilson is a doubt for Sunday (against St Johnstone)," said the Celtic boss.
"But I am hoping they will start training on Monday or Tuesday next week and if they do then they will be in contention."