Mazzarri said: "I have always trained young people, who have then exploded. I value youngsters, they are important and are a part of the satisfaction of being a Coach.
"But, we need to now see if they are ready to stand up, as is being called for in Naples, and contribute in Serie A at the highest level.
"This has to be proven. Potentially they may have important qualities, if they are ready to handle the big time then this is the time to tell us.
"Insigne and Vargas are two unknowns - we will all help them to take an important step in their career.
"Insigne grew up here and I gave him his debut in Serie A. Then, he did well in Serie C, ascended to B and has also been good.