The defender moved to Old Trafford five and a half years ago from Sporting, but struggled to play consistently for United as injuries hampered his stay at the club.
His contracted is set to be mutually terminated so that he can switch to Boca for free, the Daily Mail reports.
Ole Gunnar Solskjaer is well stocked in defensive positions and remains keen to move on one more player, with Phil Jones set to depart in the summer with time running out in this winter window.
United are reportedly interested in Sevilla centre-back Jules Kounde and RB Leipzig’s Dayot Upamecano, but the club are unlikely to sanction a big-money signing without departures first.
Brandon Williams will stay at the club rather than go out on loan in order to provide competition and back-up for Aaron Wan-Bissaka, while 18-year-old Facundo Pellistri has gone out on loan to Alaves.