Mikey Moore, 17, midfielder Lucas Bergvall, 18, defender Archie Gray, 18, and 19-year-old striker Will Lankshear all started on the night. Spurs won through goals from Pape Sarr, 22, and Brennan Johnson, 23, goals.
"I thought Mikey was outstanding," said Postecoglou. "It’s brilliant for a 17-year-old to play 90-plus minutes in a European away tie. He handled it superbly. I kind of knew he would and it’ll help his growth as a footballer.
"If you look at the Premier League, how many 17-year-olds are actually contributing and Mikey is already, which shows he’s got something special - but we’ve got to be really careful how we develop that."
On the other youngsters, Postecoglou added: "They’re part of our first-team squad, not because I want young players, it's because they've earned that spot. We can't discount the fact Archie is 18, Lucas is 18.
"Archie was brilliant. We asked him to play in two different positions and it's incredible how he adjusts. Lucas worked hard and Will was unlucky with a couple of moments when we could have got a goal.
“These guys are there because they've earned their spot, but they're an important part of our development."