Manager Ronny Deila says Celtic will have to rebuild Efe Ambrose's confidence after his part in conceding goals to Fenerbahce on Thursday night.
The Parkhead boss stressed that they "win as a team and lose as a team", after squandering their two-goal lead to finish up 2-2 in the Europa League.
Fernandao took advantage of some sloppy defending by Ambrose, 26, to score twice for the Turkish side.
"Everybody understands that he did a mistake in the first goal," said Deila.
"We are a team and we have to build him up again as he's of course very, very sad that he did that mistake.
"But as a central defender and a goalkeeper you are vulnerable to mistakes and if you make them it costs you your points."
Celtic were leading their Group A game against the Turkish side thanks to goals from Leigh Griffiths and Kris Commons.
But a back header two minutes before half-time by Nigeria defender Ambrose came up short, allowing substitute Fernandao to pull a goal back for the visitors.
And, after the break, the Brazilian striker escaped the attention of the Celtic defender to level from a corner.
Describing how his player feels in the wake of the result, Deila added: "He was very down, of course, but he sees that he has improved a lot and feels that he is in good shape.
"He was the best player available to play that match. He played well for two or three matches and he has a lot of experience.
"We know and he knows the issues that he has to work on and we are working on them every day.
"As I said, 98% of what he did last night was good, but of course you remember the two per cent that wasn't at the level you want it to be."
Ambrose is suspended for Sunday's Scottish Premiership trip to Hamilton Academical, which the Norwegian boss described as "the worst thing he needs".
"You have to get back again and play a good full match again," Deila explained. "The worst thing he needs is to remember the last game. Football is like that, you remember the last thing you have done.
"He wants to play football again. He will be with the Nigeria team and will come back after that and be ready to play for Celtic."