Juve's formidable defence held mighty Barca to a 0-0 stalemate in Wednesday's quarterfinal return match at the Camp Nou, after the defending Serie A champions stunned the Catalans 3-0 in the first leg.

And Allegri told Mediaset Premium that only only the very best version of the Bianconeri could've accomplished the feat.

"We have to compliment the lads for all they are doing this season. It's a step forward, a deserved qualification against a top level opponent," Allegri said after the match.

"We did very well defensively, less so in attack where we failed to make the most of very promising counter-attacks. We were under the normal amount of pressure here, but it was a decisive step on the road to Cardiff.

"Barcelona failing to score goals over two legs is almost unheard of. The lads need to realise that they can do even better and we are slowly improving.

Gonzalo Higuain attempts a shot on goal in Juventus' Champions League second leg against Barcelona.

"We mustn't get ahead of ourselves, but it's right to feel enthusiasm and tomorrow we need to focus on Serie A. Celebration? Well ... it's the decisive moment of the campaign, these lads have a great sense of duty and professionalism. What I like best is that I don't need to tell them off about that.

"We should've been calmer and sharper when spreading their play, but it's not easy to do that here, as Barcelona are a completely different team on home turf. They move the ball around so quickly and only a great Juventus could've qualified.

"I am happy with what the lads are doing, but the key is not to maintain current form, instead aiming to improve it. Everyone was extraordinary tonight and when Andrea Barzagli came on it felt like we could've played for a whole day and not conceded."

Allegri's switch to a 4-2-3-1 formation this season has sparked his attack, allowing him to fit the likes of Dybala, Gonzalo Higuain, Juan Cuadrado, Mario Mandzukic and Miralem Pjanic in the same XI.

"The club has worked very well to bring in players of quality who had different characteristics and it was my job to put them in a position to give their best," he said.