Buffon will probably retire in 2018 after his last world cup, when he'll be already 40.
Neto is still young, would be in a prime position to get the vacancy at 28/29, an ideal age for a keeper, and if he's good he'll have the starting spot for a good 5/7 years. It's a long time.
So I like his decision, and I love his signing by Marotta. Very reliable backup, with good projection for the future.
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But yes, he'll have to be very patient and be a backup for 3 years. Hopefully he will have what it takes to be OK with only playing in Coppa for 3 years.