Left winger: Ousmane Dembele
Ernesto Valverde has started to offer Dembele more opportunities this time around, although he has still not nailed his position in the starting XI. But with Messi out injured, he will need more attacking firepower and Dembele is perfectly capable of it.
He has struck thrice already this season and also averages over two key passes per game. The 21-year old links up well with his attacking counterparts too. If started on Sunday, can have a pivotal role in the outcome.
Right winger: Gareth Bale
Given his high-flying start to the campaign of scoring and/or assisting in each of the first four games, Bale was supposedly gearing up to succeed Ronaldo's throne; something that he was touted to do since joining Real Madrid in 2013.
But just like the rest of his team, his form deteriorated too soon after and yet again, succumbed to a fresh bout of injury. He returned for the Champions League clash against Viktoria Plzen in the midweek, and looked fairly convincing, assisting Marcelo for a goal too. But to score against Barcelona, he has to bring his A1 game to the fore.
Striker: Luis Suarez
Karim Benzema's atrocious run in front of the net leaves the door ajar for Suarez, who's although been only marginally better. The Uruguayan too has somewhat struggled to find his shooting boots, but has at least made his presence felt up front with four goals and assists each in La Liga.
He ended his six-game goalless streak in the 4-2 defeat of Sevilla last weekend from the spot, and will now look to continue in the same vein in the Clasico, in which he's netted six times and assisted thrice in 11 appearances.