Neil Lennon's side failed to build on their historic win over Barcelona as Benfica's 2-1 victory left both side's hopes of reaching the knockout stages on a knife edge.
Champions League: Lennon disappointed by 'nervous' Celtic as last-16 hopes remain in balance
Neil Lennon admits Celtic's hopes of qualifying for the knockout stages of the Champions League remain in the balance after a 2-1 defeat to Benfica.
The Scottish champions are guaranteed a Europa League spot after Barcelona's 3-0 victory over Spartak yesterday
Qualification for the last 16 of the Champions League, however, will require them to achieve a better their home game against the Russian side by a better result than Benfica manage at the Nou Camp.
And the Celtic coach, who masterminded the side's win over Barcelona two weeks ago, admits it may prove a tougher challenge than expected.
"I think Benfica are capable of getting a win in Barcelona, for they are an excellent side.
"But we have to make them do that.
"I don't know what kind of mindset Spartak will be in, they might want to spoil our party, we have to be totally focused.
"What we have to do is win at home and make Benfica win in the Nou Camp which is no easy feat.
"The onus is on us to do that.
"The squad is stretched, we hope to have a few more players back for that game.
"No one gave us a prayer coming in to this competition, these players have been exceptional, they have made a name for themselves and we are still in with a good chance of qualifying."
Celtic were on the back foot for much of the game at the Stadium of Light.
Ola John gave the home side the lead in the seventh minute before Georgios Samaras levelled in the 32nd minute from a Charlie Mulgrew corner.
Defender Ezequiel Garay restored Benfica's lead in the 72nd minute to ultimately, and deservedly, leave both sides on seven points after five games.
Lennon admitted afterwards the result was a fair reflection of the Glasgow side's performance.
"I am disappointed," he said. "I thought there was a lack of composure to our play at times, a bit of nervousness which is understandable.
"Our passing was poor and we weren't decisive enough and it was a poor second goal to lose.
"We weren't at our best but you have to give credit to Benfica for the way they played."
Benfica coach Jorge Jesus will take heart from Celtic's win over Barcelona at Parkhead earlier this month when he takes his side to the Nou Camp.
"It was a great win for us," he said of his side's performance against Celtic. "We didn't deserve to be drawing at half-time, they scored with a set-piece as we thought they might. But we played very well.
"Now we are playing on the biggest stage in the world against the biggest team in the world.
"But we have shown we are more of a team than Celtic and they beat Barcelona so nothing is impossible.
"If we have a bit of luck we can do it."
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