I totally reject the premise that Juventus’ problem in the Champions League is their 3-5-2 formation. Totally and without reservation. Formations, provided one has the players to execute and the tactical nous to make adjustments to a particular player’s role (go a little wider or tuck in a little more; attack more or stay back; mark or press this opposing player), are beside the point.
Manchester City has struggled in the Champions League with a far more expensively assembled lineup, yet no one is blaming Manuel Pelligini’s formation on their shortcomings.
The Champions League is difficult and Juventus, with the exception of their goalkeeper, the ageless Gianluigi Buffon and Andre Pirlo, and their tireless terrier of a striker, Carlos Tevez, does not have many players with experience in the latter stages of the tournament. Switching to a 4-2-3-1 or 4-3-3 or 4-3-1-2 or a 3-3-1-3 (shout out to Marcelo Bielsa on that last one) is not the answer. Luck, a few new players, and some more luck are the answer. I would argue that they failed in the past because Juventus didn’t sufficiently rotate over the season, but it’s certainly not about a particular formation, unless it’s not properly executed.