Boss Brendan Rodgers praised his Celtic young guns and Eoghan O'Connell in particular after the Hoops booked a place in Friday's Champions League play-off draw.
A dramatic last-gasp 2-1 win over FC Astana at Parkhead on Wednesday night gave Celtic a 3-2 aggregate win over the Kazakhstan side in the third qualifier.
Irish defender O'Connell, 20, made his European debut last week at the Astana Arena and he kept his place with experienced Nigeria international Efe Ambrose dropped altogether in a rearguard reshuffle which saw 20-year-old right-back Saidy Janko come into defence where 19-year-old Kieran Tierney was at left-back.
On-loan winger Patrick Roberts, 19, also started and 20-year-old French striker Moussa Dembele came off the bench to score a stoppage-time penalty winner for his first goal in green and white after joining the club in the summer, after Leigh Griffiths' spot-kick on the stroke of half-time was cancelled out by substitute Agim Ibraimi.
The youthful influence in what was a crucial victory for the Scottish champions pleased Rodgers.
"If you think, we had a 20-year-old at right-back, a 19-year-old at left-back, and a 20-year-old at centre-half, young boys further up the team and a young boy comes on and scores a penalty so at this level it is a very, very young team," he said.
"But they are gaining experience and you have to give time to talent, encourage it, be supportive of it.
"They are going to make mistakes but if you trust them and stick them out there, hopefully you will get performances but he (O'Connell) in particular was very good.
"I thought he was outstanding. I have said before, I have been really impressed with him.
"For a young player who has been at Oldham and Cork on loan, to be put into the games he has been put into and shown that composure - he is a wonderful young footballer.
"He dominates in the air, so he wins his headers but if you want to reach the highest level you can, you have to be able to dominate the ball and as a kid he passes it very well.
"He has an in-built brain for the game and I am looking at his temperament.
"I see him in training. I don't know how many games some players have played but if they show that temperament and composure, like he has over the couple of games, he is only going to get better and better."