Speaking on talkSPORT, Graeme Souness said: "Manchester United have got to win the FA Cup, but they've got a monster job on their hands.
"Even if they do, Erik ten Hag wouldn't keep his job. I think that their minds were made up not long after Sir Jim Ratcliffe came in [as co-owner].
"The manager's job is to get the best out of the group of players and right now you would say that's not happening at Manchester United.
"Listen, I'm not calling for Ten Hag to be sacked or anything but I think they [the new owners] made their mind up a month ago."
Man United are through to the FA Cup final after beating Championship side Coventry City on penalties at Wembley in the semi-final.
However, it remains to be seen whether Ten Hag will stay in charge even if the Red Devils beat Manchester City given the many issues at the club.
