The Barcelona superstar has been in impressive form this season, netting 16 goals in just 20 appearances.
But Spanish outlet Diario Gol claim Zidane’s secret weapon is Mateo Kovacic.
Barca take on Real at the Bernabeu on December 23 at midday with Zidane looking for his side to close the gap on the La Liga leaders.
Kovacic will be back in time for the clash after recovering from injury.
And the Croatian has been instrumental in the past in helping to stop Messi.
Kovacic was hugely impressive in the Spanish Super Cup at the start of this season.
Real Madrid have lost the last two El Clasico meetings with Barcelona at the Bernabeu and will be determined to change that.
Ernesto Valverde’s side currently sit top of the table, eight points clear of their arch rivals.
Valencia are the closest challengers to Barca, just four points behind.
Messi and co have yet to experience defeat in La Liga this season.