Been thinking a lot about the midfield situation for this match and ironically I feel it might be better to start with one of the retard brothers as opposed to Vidal.
The way I see it, Vidal would be fired up and all that, but his body simply isn't up to it anymore. Despite his tenacity and his best efforts, I feel like Liverpool would just run circles around him, especially in transition, and drag him out of position over and over again. One slightly late challenge gets him booked and from there on he becomes a liability.
Gagliardini on the other hand is more static and less rough than Vidal. He doesn't hurl himself into challenges full pelt nor does he press with as much aggression. There's less chance he'll pick up a booking and if he just screens well and holds his positioning with a degree of discipline, he might act as an obstacle to Liverpool's passing game. Albeit, to the same degree of difficulty of a training cone in a routine drill.
Finally, Vecino would simply be absent from midfield, as he always is, but this might help us in transition. In the rare moments we win back possession and lump a hopeful long ball forward, Vecino could help us by providing another body up front and attacking the Liverpool box. Make no mistake, this is a 99% useless strategy but I am always up for those.