The FA Cup has not always been enough to save Manchester United managers.
Tommy Docherty won one in 1977 and was sacked the next month. Louis van Gaal won one in 2016 and was sacked the next day.
So the current incumbent, Erik ten Hag, will not rest easy, not yet. With new part-owners at Old Trafford tracking and watching his every move, Ten Hag will need steady progress on all fronts between now and the season's end if he is to be invited to stick around. This second campaign of his tenure has simply raised too many questions about his suitability.
Still, this was a big step forward. A tricky Cup tie won against a sticky opponent, United are in the quarter-final. Once there they will face Liverpool. Indeed, thanks to the unfathomably stupid idea to conduct the draw for the next round before half of the round five ties had kicked off, United knew this before a ball was even rolled here. Not a great reward for their work, granted, but they will be at home against their great rivals and they have beaten them at Old Trafford before in recent times. It could happen.
Here at the City Ground, United were not at their best but they were significantly better than they had been in losing at home to Fulham at the weekend and indeed when being turned over here just after Christmas in the Premier League and that transpired to be enough.
Casemiro scored late to earn Man United a 1-0 win over Nottingham Forest in the FA Cup
The Brazilian scored a flicked header at the near post from Bruno Fernandes free kick
Casemiro's late effort saw Man United set up an FA Cup quarter-final with rival Liverpool
They traded chances with Nottingham Forest throughout a good game and won it late on when the Brazilian midfielder Casemiro stooped to head a free-kick from Bruno Fernandes through the legs of goalkeeper Matt Turner in front of the away support.
The goal was subject to a VAR check and replays appeared to show United's Rafael Varane standing in an offside decision as he blocked Forest midfielder Ryan Yates from moving towards the ball.
It seemed to be a similar, if not identical, situation to the one that saw a Liverpool goal ruled out in the Carabao Cup final at Wembley against Chelsea. This time, though, referee Chris Kavanagh was not invited to take a look at the pitchside monitor by the VAR team and the goal stood. Consistency? Not a chance. But we have long since given up on that haven't we?
But did United deserve this anyway? It was touch and go throughout but they probably did. They created some good opportunities and Forest goalkeeper Turner was one of his team's best players. Doubts remain over the likes of the Brazilian winger Antony - given a public endorsement by Ten Hag beforehand but failing to last 90 minutes - and indeed Marcus Rashford who continues to look out of sorts, especially when playing centrally as he did here.
There was an endeavour and a desire here, though. Such qualities are basic, granted. They should come as a given when players pull on a United shirt. But it hasn't always looked that way in recent times.
The atmosphere by the banks of the Trent added to the occasion. United seemed to feed off it as much as their opponents in the early stages and could have been ahead as Antony struck the bar with a rising shot and Scott McTominay headed a Diogo Dalot cross goalwards, working Turner for the first time. The American was to deny the Scot again later in the half - this time with a sharper save to his left - while Rashford drilled a shot over.
The recalled Antony went close for Man United in the opening minutes by hitting the crossbar
Scott McTominay headed straight at Nottingham Forest goalkeeper Matt Turner in the box
The midfielder forced a diving stop from Turner after meeting another Diogo Dalot cross
McTominay's two efforts were the best chances created by Man United during the first half
Forest were not besieged, though, not all. With young Kobbie Mainoo rested for this one, Casemiro lacked security in the middle and too often Forest were able to break through United from deep positions.
With three forwards playing in red, Forest carried a threat. Twice Taiwo Awoniyi got behind United's emergency left-back Sofyan Amrabat to work Andre Onana with cross shots while Forest also won a number of corners.
The start of the second half was the home team's most productive period, however. Awoniyi brought a low save from Onana to his left before Divock Origi stung his palms with a thunderously struck right foot shot from 15 yards.
Over the course of the second period, United imposed themselves more consistently. Fernandes was particularly influential.
Despite his penchant for annoying everybody who doesn't support United = and some of those who do - he is a terrific footballer. Here he curled one shot over and then provided the late free-kick from which Casemiro stooped to conquer.
Afterwards Ten Hag was unusually forthright, suggesting Fernandes was too often victimised on and off the field.
Nottingham Forest created chances of their own throughout an entertaining fifth round tie
Marcus Rashford saw a penalty appeal waved away by referee Chris Kavanagh
Tempers flared in the closing stages with Felipe confronting Fernandes in stoppage time
The victory eases pressure on Man United boss Erik ten Hag ahead of the Manchester derby
'Forest were targeting him,' said the United manager.
'I see social media criticise him. It is pathetic. He has a serious injury. He continued to play on Saturday and then also he fought to be part of this game. He has a very high-pain threshold. It shows his leadership.'
Ten Hag's attempt to position his captain as one of football's great warriors will amuse many. But for now that does not matter very much. Ten Hag's head remains above water.