Brendan Rodgers and Scott Brown were relieved and disappointed in equal measure as Celtic progressed to the Champions League group stage despite defeat at Astana.
Celtic had thumped their opponents 5-0 in the opening leg last week but found themselves 4-1 down with just over 20 minutes remaining in Kazakhstan as the hosts went in search of the three more goals they needed to complete the most remarkable fightback.
Astana squandered chances to pile further pressure on the visitors, who then scored two late goals on the break to dismiss any lingering doubts and secure an 8-4 aggregate win - the highest-scoring tie in Champions League play-off history.
Celtic - losing a competitive fixture for the first time since they were beaten by Barcelona in November - will now take their place in Thursday's draw for the group phase, leaving Rodgers to analyse an evening of contrasting feelings.
"On the night it's mixed emotions because we didn't defend well enough and our possession at times wasn't good enough either," he told BT Sport.
"We were too loose in our passing and we gave away a poor first goal. I thought we'd get through this [qualifying] campaign without anxiety!
"We were trying to plug gaps, credit to the players, they were on the ropes for 15-20 minutes there. It's disappointing tonight but across the campaign the players have been first class.
"They deserve to qualify and we look forward to the draw."
Captain Brown added: "[We were] not so good coming over here, 4-3 was an exciting game for the neutral but not so much for us.
"It was a game of basketball, that's not like us, we're usually very tight and we were a bit too open today. European football is never going to be easy, to win 5-0 at home shows you what you need to do.
"Coming here is always hard on an astroturf pitch but we're a little bit disappointed with ourselves."