There was a time in Milan where both Nesta and Pirlo played together and from what I recalled Nesta and Pirlo was on the same team when Milan won their last Champions League Finals during 2006-2007 season. From what I can tell Nesta might be one of the best candidates out there as assistant as Nesta previously became captain of Milan shortly after Maldini retired and he has a lot of experiences both within the league and international plays. However I don't think Nesta will be prepared to adapt such a big leap going from coaching and managing a small team and then managing the top club in Serie A, he might not be able to adjust well.