Just putting the question out there now.
We play Blackburn tomorrow, away in the FA Cup where we surely want to win and at least avoid a replay. We play St. Etienne away on a Wednesday where the tie is all but over. Why would we rest a plethora of players in both games instead of just the latter, which is over. Out-and-out first XI players who play this game tomorrow will have a week long rest before the final against Southampton. Hell, some of them won't even need to travel to France so will be even more rested.
To me, it just makes sense to stick with the majority of the first-team tomorrow, then bring in the squad players against St. Etienne to rest the first XI for Southampton. Surely even players like Zlatan, Pogba, Martial, Mata etc aren't going to need to be left out of playing a game for a nine day period.
I do get that for this season, the FA Cup is bottom of the list in terms of goals this season behind Top 4, League Cup, and the Europa League. But, we're in the Final of the League Cup, Top 4 is very much alive and we're not needing to bother about that for a couple of weeks. We are all but through to the next round of the Europa League already even if we rest our entire first team... So, we might as well just go pretty much full strength here (and by that I still mean there will be about four changes including de Gea coming in to make the side stronger anyway) and progress.
Jones, Rojo, Shaw, Darmian, Fosu-Mensah, Schweinsteiger, Fellaini, Young, Rashford, Rooney, Lingard etc will get the minutes in France and maybe one or two + some as subs tomorrow still.