Brendan Rodgers praised his Celtic side's "huge achievement" after they dramatically secured a place in the last 32 of the Europa League.
The Scottish champions finished second in Group B despite losing 2-1 to last year's semi-finalists Salzburg.
It took an unlikely Rosenborg equaliser in Leipzig to push Celtic over the line, but Rodgers was delighted with his side over the six games.
"Huge congratulations to my players," said the Celtic manager.
"This campaign was over six games, so to finish in a really tough group with nine points and qualify is a huge achievement.
"You have two Champions League teams in Salzburg and Leipzig, the investment, everything that goes into their organisation which is based to succeed.
"So for us to come out on top against a high-ranking team, Leipzig, from one of the top European leagues, is another big step in the progress of our players."
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'Still a lot to improve on'
What started out as a disappointing European campaign has blossomed into one of positives for Rodgers.
After failing to qualify for the Champions League for the first time in his tenure, the Northern Irishman has guided Celtic to two wins over Rosenborg and a victory at home against RB Leipzig during the Europa League group campaign.
However, that effort looked like counting for nothing as Celtic trailed Salzburg with Leipzig clinging to a lead in Germany prior to Tore Reginiussen's late leveller that robbed the Germans of two crucial points.
"It was mixed emotions for me," said Rodgers. "The one thing I looked for tonight was performance. We didn't play well. It's as simple as that. I was very frustrated.
"To come out of it with nine points shows the achievement over the course of the games. You knew by the end the score had finished 1-1. It's mixed really. There's still lots of areas we can improve on."
Celtic 'need a couple of quality players if they want to progress' - Analysis
Former Celtic striker Scott McDonald on Good Morning Scotland:
"The Rosenborg games were ones Celtic expected to win but the Leipzig result was probably the best performance under Brendan Rodgers in Europe during his time at Celtic. That is ultimately what has got them through - albeit with help from Rosenborg.
"To reach the last 32 is a fantastic achievement for Celtic and Scottish football as a whole. Anything else beyond that now is a huge bonus.
"Brendan has talked about strengthening in January and hopefully he will have two or three more in. Filip Benkovic looks as if he might stay until the end of the season, which is fantastic news.
"If that happens, there is a possibility if Dedryck Boyata goes in January, that frees up even more money for Celtic to attack that transfer window.
"It's very difficult to bring in the quality you need in January, but they will certainly need a couple of quality players if they want to progress in the Europa League."