Ole Gunnar Solskjaer's men ran amok at Old Trafford on a night which started with Saints teenager Alexandre Jankewitz being shown a red card less than 90 seconds into his first start.
While there was no arguing with that given the terrible challenge on Scott McTominay, it’s understood Southampton are appealing against the decision to send off Bednarek for a foul on Anthony Martial.
READ MORE: Is there ever any excuse to lose 9-0?
Video assistant referee Graham Scott instructed Dean to watch replays of the incident on the pitchside monitor, with the referee keeping with his decision to award a penalty and also sending off the bemused centre-back.
Bednarek claimed "Martial said it's not a foul" as he left the pitch, with Bruno Fernandes scoring the resulting 87th-minute penalty before Martial and Daniel James wrapped up a record-equalling Premier League win.
Injury-ravaged Saints are hoping that the Poland international, who scored an own goal in the first half, will have his one-match ban rescinded and be available for Saturday's trip to Newcastle.
It’s understood the Saints hierarchy are angry and frustrated about the officiating of Dean and Lee Mason in recent days but have stopped short of formally requesting that they are not in charge of their matches.
Mason was fourth official at Old Trafford on Tuesday, having officiated Southampton's contentious 1-0 loss at home to Aston Villa on Saturday evening when he missed Matty Cash's handball from an early Stuart Armstrong strike.
Dean acted as VAR that night and reviewed the decision but did not award a penalty as he decided the ball had flicked off the defender's thigh first.
Danny Ings also saw a late leveller against Villa ruled out the narrowest of offside calls, with Dean clearing the on-field decision. Che Adams also saw a narrow offside call go against him when scoring at 4-0 on Tuesday night.
Captain James Ward-Prowse did not want to talk too much about the decisions following the 9-0 loss to United, instead focusing on the need to bounce back like Saints did after losing by the same scoreline to Leicester in October 2019.
"A difficult night for everybody," he said. "Obviously difficult from the start but we have to pick ourselves up from this disappointment and look to the weekend.
"We've got a lot of games coming up and we've got a chance at the weekend to show a reaction.
"We know how difficult this can be, but there's no point in us dwelling and thinking too much about it. We have to pick ourselves up and go again.
"It's a difficult game at the weekend and everybody is going to be looking at us now for that reaction and we've got to go out and show it."
Put to him the big decisions did not go Southampton's way, Ward-Prowse said: "Those decisions, you know, we leave that for everyone else to look at. We don't need to... you know, it's clear for everybody to see.
"But, like I said, we have to pick ourselves up. It's a disappointing night but we have to go again."
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies