Acid test for Juventus

A potent new attacking formation that has sent Gonzalo Higuain towards another top scorer's award faces the acid test Wednesday when Juventus take on Porto away in the last 16 of the Champions League.

Juventus, beaten 3-1 by Barcelona in the 2015 final, are en route to a record sixth Serie A crown and remain many pundits' favourites to challenge the likes of Real Madrid for the trophy in Cardiff next May.

Massimiliano Allegri's Serie A league leaders head to Porto's Estadio do Dragao as favourites, but aware that they also ended Roma's hopes of even qualifying for the competition in clinical fashion last summer.

"Juventus are a top side who have made it to the final of the Champions League recently, so they will be a challenge for us," Porto president Pinto da Costa was quoted as saying in Corriere dello Sport.

"But Roma were also favourites against us, and in the end we won 3-0."

Allegri's decision to ditch his tried and trusted 3-5-2 for a more attack-minded 4-2-3-1 has seen Higuain, thanks to support from Juan Cuadrado, Paulo Dybala and Mario Mandzukic, pull level with Roma's Edin Dzeko at the top of the Serie A charts on 19 goals so far.

But while the Juventus front line is firing on all cylinders, Porto have reason to be targeting a makeshift Juve defence that could be missing key components in Andrea Barzagli and Giorgio Chiellini.

Both remain doubtful due to recent injury niggles, meaning either Daniele Rugani or Mehdi Benatia could partner Leonardo Bonucci in central defence.

Allegri's switch to a flat back four means Stephan Lichtsteiner, Dani Alves, Kwadwo Asamoah and Alex Sandro -- who are all adept as wingbacks in a five-man midfeld -- are all available for the left and right-back positions.

On Friday Allegri said: "Unless some strange things happen in the meantime, we will deploy a 4-2-3-1 in Portugal."

Both Rugani and Lichtsteiner were completely rested for Friday's 4-1 win over Palermo, in which Dybala hit a brace and Higuain hit one. Mario Mandzukic was also completely rested, suggesting he is a definite starter on Wednesday.

Allegri's two holding midfielders are likely to be Miralem Pjanic, the side's free-kick specialist, and Germany midfielder Sami Khedira.