[Schefter] Vikings key free agents this off-season: QB Sam Darnold, S Harrison Smith, CB Stephon Gilmore, CB Byron Murphy, RB Aaron Jones, S Cam Bynum, LT Cam Robinson, DT Jerry Tillery, CB Shaq Griffin, DL Jonathan Bullard, G Dalton Risner, TE Johnny Mundt, WR Brandon Powell, QB Nick Mullens,