Brendan Rodgers has bemoaned his Celtic side lacking aggression at the back after they lost 3-0 in Russia to Zenit St Petersburg to exit the Europa League at the last 32 stage.
It took just seven minutes for Zenit to take the lead on home turf with the Celtic defence failing to stop Branislav Ivanovic from powering a header past Dorus de Vries from a corner.
Matters then got worse for the Scottish champions in the 26th minute with De Vries at fault as he appeared to misjudge an effort from 25 yards out by Daler Kuzyaev, whose effort put Zenit 2-0 up.
Celtic brought Tom Rogic on at half time and were hoping to fight back in the second half, but Zenit grabbed a third on the hour mark with Aleksandr Kokorin sharper than Mikael Lustig to connect with a cross from Ivanovic and turn it into the back of the net.
The visitors threw on Scott Sinclair in the 62nd minute and Charly Musonda in the 71st minute, but Zenit were always comfortable and claimed the 3-0 win on the night to progress 3-1 on aggregate.
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Rodgers believes that his side were not good enough at the back, while he also levelled the charge that they failed to be brave when needed.
"Defensively, we lacked aggression, especially in the first half", Rodgers said at his post-match press conference.
"We didn't defend forward well enough. But, at 2-0 down, we were still in the game and we had to show bravery.
"Second half, we started okay, but we again concede the possession too cheaply.
"Across two games, we were much better than them in the first game."
And Rodgers thinks that a lack of courage was the difference between his side crashing out and progressing.
"In this one, if we had showed more courage and more belief, we could have got a result.
"I think there's still an awful lot of work for us to do, but there have been a lot of positives for us in both competitions."
