The worrying thing for Manchester United is that while Manchester City had moments of brilliance at Old Trafford, they did not really have to do much to beat them 3-0.
It is one thing to lose because of your opponents’ superior quality, but if it happens because you are disorganised defensively and cannot match them physically then that is a huge concern.
This is actually nothing new for United – when I have watched them recently, I have felt like they are too easy to play against and get through.
It happened last season too, but then we saw a more pragmatic approach from them in certain fixtures – including their win over City at Old Trafford in January.
That is the kind of resilient and tenacious performance I was expecting from them this time too, but when I saw the United line-up I was worried for them.
I have said before that when they have the likes of Christian Eriksen and Bruno Fernandes in their team, who are both really gifted technical footballers, it means they lose something defensively.
That is fine in some circumstances, but they both started on Sunday against a team where you really need everyone to be disciplined out of possession too.
We have seen Arsenal and Newcastle beat City in the past few weeks after matching them physically, but United never came close to that – they needed more legs, more energy and more tenacity out there.
What next for United?
I know Erik ten Hag has some injuries to contend with, but it does not seem like there are enough repercussions for some United players if their intensity is not at the required level.
There have been games this season where he has made changes at half-time, so fair play to him for that, but generally the senior players like Fernandes, Eriksen or Casemiro do not get dropped very often for not doing the work.
That just would not happen at City, or Liverpool or Arsenal either. If their players do not do their jobs properly the way their managers want, they are gone from the team.
Ten Hag said before the game that he was happy with his team’s pressing and defensive organisation but I have watched United in the past few weeks and I cannot believe that.
Against FC Copenhagen and Brentford, United did not produce satisfactory performances, even if they got a positive result in the end.
On Sunday, they did win the ball back in good areas in the first half, and forced City into mistakes, but you have to maintain that for 90 minutes. They couldn’t, and we saw what happened.
If he wants to play this way, then Ten Hag has got to get his best athletes on the pitch – the players who are going to do the running for him.
At the moment, it appears that to be a little bit lackadaisical and not track back is acceptable, and so is whinging at your team-mates or throwing your arms in the air when things go wrong.
Overloads should be easy to stop
It is always a balancing act as a pundit when you are critical of a team, as well as being complimentary about the side they are up against, but I feel I have to do both here.
We know how good City are, and how they wear you down with their movement and their technical ability. On top of that, their decision making is as good as it gets, all over the pitch.
Against United, they knew when to play through the lines, when to clear their lines, when to go for goal and when to come back and frustrate the opposition, until the time was right to hurt them.
That sounds easy, but to have everyone in the team on the same page about all of that is very rare, and it was phenomenal to watch.
At the same time, though, United helped them massively and made it far easier for them than it should have been.
It was not as if City kept opening United up through amazing skill, although there were glimpses of that – there was one team move in the second half where Andre Onana denied Erling Haaland, which would have been goal of the season had it gone in.
Instead, a lot of United’s problems came simply from them not doing the basic things you need to do in any game.
Overloads in wide areas in particular were a huge issue for them. It mainly happened on the left, with Bernardo Silva, Josko Gvardiol and Jack Grealish all playing their part.
You had the brilliance of Silva, bursting through from central midfield areas and running inside to out, plus Josko Gvardiol getting forward from left-back too.
Then of course there was Grealish, whose ability to keep the ball gave those players time to get up the pitch and run past him, before he released the killer pass.
City kept on creating chances down that flank and Haaland should have scored from one late in the first half before he got City’s second goal after the break by finishing off a similar chance.
That will be the most disappointing aspect of the defeat for Ten Hag when he watches the game again, because it should have been easy to stop.
Teams cannot keep getting overloads like that unless someone is not staying with their man.
You do not need to be a tactical genius to deal with it – you just need to have people following the runners, and tracking back.
Danny Murphy was speaking to BBC Sport’s Chris Bevan.
Olivia Martin is a dedicated sports journalist based in the UK. With a passion for various athletic disciplines, she covers everything from major league championships to local sports events, delivering up-to-the-minute updates and in-depth analysis.