El Clasico: Barcelona vs Real Madrid - 3 things to watch in Copa Del Rey first-leg

#3 Sergi Roberto's test of mettle against Vinicius Junior

Vinicius Junior - Real Madrid's unlikely hero tomorrow?

Barcelona's utility man Sergi Roberto is one those few players besides Messi to have consistently turned up for El Clasico in recent times. In fact, he's engineered four goals in the last three games versus Real Madrid, including two in the historic 5-1 drubbing last October.

His buccaneering runs down the right flank adds an extra layer of attack to Barcelona's already fearsome attack, and he's proved to be a thorn in Madrid's face recently. But his form in the current season as a whole has been erratic. His defensive work has not been on par while his penchant to drive forward has often left too much space at the back for opposite teams to exploit. The 4-3 loss to Real Betis perfectly sums up this theory.

Roberto would be up against Real Madrid's Vinicius Junior tomorrow, the Brazilian wonderkid who's on a good run at the moment. In the Copa Del Rey, he's scored twice and assisted a staggering seven times as Vinicius has proved to be his side's secret sauce in this particular competition. And he can pose a stern challenge to Roberto too.

If provided with space and time, the 18-year old can cause serious problems, and Roberto may have to limit his forward forays here.

Vinicius was not in action the last time Real Madrid and Barcelona crossed swords as he didn't even make the cut into the squad. But he's come a long way since then and the Brazilian is now one of the foremost names on his side's teamsheet.

Whilst most of the key battles would circle around the big names in both camps, this one too could prove to be significant to the outcome of the tie.