Ronny Deila lamented Celtic's defensive frailties in the home loss to Molde but insists they have a "realistic" chance of progress in Europe.
The Norwegian side claimed a second successive win over Deila's men, prevailing 2-1 in Glasgow.
However, Celtic can join Molde in the last 32 if they beat Ajax at home and Fenerbahce away.
"Again we conceded two easy goals," said Deila. "We can beat Ajax here and we can beat Fenerbahce down there."
Mohamed Elyounoussi volleyed Molde in front but Celtic levelled when Nir Bitton's shot deflected into the net off team-mate Kris Commons.
Daniel Berg Hestad became the oldest scorer in a Europa League tie, the 40-year-old stretching to knock in Molde's winner before the break.
|Celtic managers' results in Europe - first 24 games|
Bitton's dismissal for a professional foul on Ola Kamara completed a miserable night for Celtic.
"I don't think we got up to the tempo and level we had on Saturday [in the 3-1 win against Aberdeen]," said Deila.
"We had a lot of chances ourselves, big chances. I'm not very pleased with the performance. It's individual mistakes. That's disappointing.
"We, all the time, try to analyse what we're doing. Try to do things even better. We are not satisfied with what we did today. That said, we still have a chance to go through. It's realistic, of course."
Deila last week hit back at his and the team's critics, stressing he only cares about the opinions of those at Celtic.
And, when asked about how his tenure at Celtic will be assessed, the Norwegian said: "It's a lot of things that I've been judged on.
"It's the results in Europe. If we lose the league, I don't think that's good as well.
"It's about developing a team that can get into Champions League and get a green line through the whole system.
"I'm going to work hard to turn this around and be ready for next year.
"We have done very well domestically. In Europe we haven't reached the level that we want to do but we're going to improve, that's what we're going to do.
"We're going to fight to the end for those six points."
The Celtic dressing room was "very, very disappointed and angry" after the match, according to Deila, who described teenage left-back Kieran Tierney's performance as "a positive thing on a dark day".
And he added: "There's a lot of talent in the squad. We haven't been good enough so far.
"Molde has been the best team. We can give some credit as well to Molde. They have won almost every game they've had in Europa League."
Visiting manager Ole Gunnar Solskjaer said of Celtic's struggle to excel in Europe as well as domestically: "It's hard when you win the league just by turning up every year.
"It's hard to keep the quality up. It's just natural that they struggle to get up to the heights they used to when they had the Old Firm derbies."