Barca won 2-0 in Turin for the first time in their history, with Mehri Demiral being sent off late for Juve.
Pirlo said, "We knew it'd be tough against a side that plays good football, that is accustomed to playing at this level, whereas we are a work in progress.
“Ultimately, it's a match that will be useful for us to grow and improve in future.
“I hope to have more players back soon, because I don't have many options and those I start end up having to play almost 90 minutes twice a week. That's not easy for them, especially when they are young and inexperienced.
“It's frustrating when you are down to 10 men, as you can't go to press them, otherwise it just ends up running on empty. That's what the lads didn't realise when we went down to 10."
He added: “Football clubs have eras, we had huge players with a lot of international experience. Now they are largely younger, so it'll take a while to get them up to that level.
“They tried to create something there, but we need to work and improve until we can play Barcelona on level terms."