actually it makes sense if the club decides to invest in a fullback, preferably someone who can play on both sides OR is more of a wingback so that ASandro (when fit) to play in that role of a left CB that is reported Pirlo likes and wants. The first player that comes to mind is of course Gossens, with three at the back he might be a very successful asset, he is more of a winger than a defender and with him and Sandro on the field team can quickly turn from back 3 to a back 4 with Cuadrado for example taking on to the RB and Kulusevski and Gossens as RW and LW.
Sadly, thats a big IF and I am not confident that a new player on that position will arrive. IF a strong and starting Juve material fullback is brought in, then sending young and promising Pellegrini to a decent Serie A side makes PERFECT sense! IF the board fails yet again and our set of fullbacks are A.Sandro/MDS/Danilo/Cuadrado then that would be depressing, even beyond depressing actually. That would make our young/fresh manager to figure out a system that doesnt require fullbacks at all so that he can compensate for the lack of quality in that department, its not impossible, but very hard to achieve, the board should be helping the coach, not making things for him even harder...