Chelsea and Andre Villas-Boas are running out of time to turn around season, says former great Gianfranco Zola

"You have to know what you're doing and you have to do it 100% convincingly."

However, Napoli boss Walter Mazzarri was taking nothing for granted.

"Chelsea, on their ground, they can easily score two goals," he said. "So, we need to go there with the right mentality.

"It's just a shame we didn't make it 4-1. We had opportunities with (Ezequiel) Lavezzi, (Edinson) Cavani, (Christian) Maggio, and we should've taken them."