Final numbers on Sam Darnold are 14-3, 4,300 yards, 35 TDs, and a 102.5 rating and 60.7 QBR. As bad as the last two games were, those are pretty solid numbers and he's still young - the same age as Kyler Murray and only a year older than Tua.
So the options are:
1) Let him walk
2) sign him to a team friendly bridge deal - something like Baker Mayfield did with TB after going 9-8 4,000 yards, 28 TDs, 94.6 rating and 55.1 QBR.
3) tag him for about 41m to be a bridge QB next year to ease McCarthy in/or trade during pre-season based on injuries around the league.
4) tag him for about 41m to be the QB for next year and listen to trade offers on McCarthy.
5) tag and trade.
I have to think the Vikings and his agent will be working the phone to find a sign and trade type deal. It would be tough to let him just walk, I would think. Teams that need a QB - Jets, Miami?, Steelers, Browns, Titans, Raiders, Giants, Saints, Panthers, Rams (if Stafford retires), Seahawks? (Smith is 35), 49ers? (if they can't get something done with Purdy?).
Anyway, I think #5 is the most likely with #3 next. With all our cap space, I don't think we can just let him walk and get nothing back (do we get draft compensation if he leaves?).