Celtic manager Gordon Strachan praised his side's mental strength after beating Spartak Moscow on penalties.
"I knew it would be an open game but I didn't know it would be that open," he told BBC Sport. "What a fantastic game.
"Our mental strength was great because they played well in the first half. So for us to do so well in the second half was fantastic.
"I felt we would win. I felt it was our time. Mentally we were strong and that helped us physically."
With Rangers also progressing to Thursday's group draw, Scotland has two representatives in Europe's premier competition.
"To get two teams into the group stages is fantastic news for Scotland," added the delighted manager.
Celtic defender Gary Caldwell, who scored his side's first spot kick in the penalty shoot-out, praised goalkeeper Artur Boruc for another superb display.
"In the first half Artur made some great saves and we always knew we were favourites going into the penalties with him in goal," said Caldwell.
"He is without doubt the best goalkeeper in the world and it's great to know that he is behind.
"The number of one-on-ones and penalties he saves says it all, the bigger the game the better he is which is a great asset for a player."
Caldwell also sought to downplay Boruc's spat with full-back Lee Naylor during the game.
"It happens at a club like this, maybe more than you think and it was the pressure of the night," said the Scotland international.
"Once you get in and sort it out it spurs you on again. It's something that's good and I don't think I would ever knock it out of anyone."
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