Pirlo starting as a regista in these kind of CL away games is suicidal IMO. It would be a tragedy. He would be completely shut down like he was most of times last year at Europe. And would cause a big defensive harm.
Marchisio has been phenomenal as a DM, I absolutely love it. World Class at this position, he's played amazingly well everytime. He's developed strenght and grinta, even beating guys up when needed.
Pirlo should be used in home games against sides which will park the bus, not in away CL battles like last one.
I know Atletico actually parked the bus, but no way in hell they would let Pirlo breath. He would just be overwelmed. He would also be a great option to go in at 65 minute, with the other team tired. With space to play he still is the legend at his position.