I think Balzaretti could be a starting player at left back. I believe he is better than Chiellini at that role and im hoping cheillini becomes a centre back.
The likes of Torricelli and Pessotto were never considered national team material when they first hit the scene for juve, which was at about Balzaretti's age. Both players were great for Juve, but rarely featured for the NT. did that mean they were not good enough? No it didnt, we won several trophies including the CL and Toyota Cup with them.
Balzaretti has been playing well and he plays with heart. No, he isn't as good as Maldini was, and he is no Zambrotta or Cole in form at left back...but he does his job and he seems to be a juve man, through and through.
The thing that made Juve so great when Lippi first joined as coach was that he made players, instead of buying the best. And he built the team based on these players that he made. Capello tried to buy the best and build the team that way, sure it was successful in Serie A (well not really in the end), but it wasn't half as good or successful as the team from 95-98.