Against Liverpool, assuming Martial is physically and mentally fit to play:
Heaton (yes, bench De Gea and I'm not a De Gea hater)
Dalot Bailly Varane Malacia
Fred Eriksen
Donny
Sancho Ronaldo Martial
Martial is vastly more effective coming in off the left than he is in a CF position and Rashford has been horrifying, so start him on the left. Let Martial work with Ronaldo and see what comes of it. Sancho has been ineffective but dropping him doesn't make sense right now.
Bruno has been poor, so Donny. Sure, Fred is an issue but unless Frenkie is a United player by this middle of this week (extremely unlikely) let's go with Fred and Eriksen in midfield. Part of me wants to Garner but Garner appears to be on his way out. The back line...well, something has to be done.
But back to Martial. Why not let him have a go at his natural position?