TURIN, ITALY - Striking a balance between scoring more while shoring up its defense will be the key if Juventus is to avoid another Champions League quarterfinal exit after cruising past Porto and into the last eight, coach Massimiliano Allegri said on Tuesday.

Juve put one foot into the quarterfinals of Europe's premier club competition last month with a 2-0 win at 10-man Porto.

The Turin giant was impervious on its way to stretching its unbeaten run in Europe to 21 games, despite failing to build on its numerical superiority after Porto lost a man before halftime.

Nuno Espirito Santo's visitor failed to pose any real threat, and any hope of an upset was ended in the 40th minute when Paulo Dybala drilled past Iker Casillas from the penalty spot after Maxi Pereira's expulsion for a handball.

Juventus cruised through 3-0 on aggregate, but Allegri was less than satisfied after the host failed to make its advantage pay in a listless second half that saw Gonzalo Higuain and Mark Pjaca waste good chances.

"In the Champions League we are scoring less goals on average than other sides with respect to the number of chances we create," said the 49-year-old Italian, who has reportedly held talks with Arsenal about replacing Arsene Wenger in the offseason.

"In defense we also have to improve. In the second half, despite our numerical advantage, we did the opposite of what we did in Porto.

"In these situations you either up the rhythm and pressure and attack or you sit back and pass the ball around till it gets boring for everybody.

"We didn't do either. We were very good in the first half, but less so in the second. Thankfully, we had our last-eight ticket practically assured, but we'll have to work on this for the future."

Although Juve remains on course for a third straight league and cup double, its real focus this season is on making amends for a 3-1 Champions League final defeat to Barcelona in 2015.

And with Barca, 11-time champion Real Madrid and Bayern Munich all possible quarterfinal opponents, Allegri has reason for concern.

Juventus accounted for Madrid in the 2015 semifinals, although the Spaniards looked formidable when cruising into this season's last eight with a 6-2 aggregate win over Napoli.

Allegri's men have fared less well against Barca and Bayern.

The Bavarians were the last team to beat Juventus at home in European competition, ending its 2013 campaign when the Turin giant was under the helm of current Chelsea boss Antonio Conte.

Allegri has already surpassed Conte's feats with the Italian champion in Europe, but he said improving on the pitch might not be enough.

"We have to be very good over our next two games if we're to make it all the way to the final. Although a little bit of luck would help as well," Allegri said.

When asked his preference, Dybala was unequivocal - although the Argentine striker was looking further ahead to the final.

"With the squad we have, and for how well we're doing in all three competitions, how can we not think about winning the Champions League?" said the talented 23-year-old, who began his career in Italy with Serie A struggler Palermo.

Agence France-Presse