The Gunners were 0-2 down in the Europa League tie, after fielding a team with several young players.
But the young Gunners rallied and they managed to get a 2-2 draw in the final game of the group stages.
And Ljungberg was delighted with the character and quality they showed to make that happen.
He told the club website: "Tremendous. Really proud of them. That's what I said to them after the game, it's a tough place to come and be 2-0 down, like you said, tremendous fans in my opinion, a great atmosphere and they showed that belief in how they can play football and their own quality.
"That shows good for us in the future, of course they need experience yes and they need to play but that heart and that fight and that belief was amazing to see from the sidelines.
"And maybe I should also mention the energy they do it with. They go and they go and they go and they don't stop."