For a huge part of my career the one ground I didn't look forward to playing in was Old Trafford. The derby games when I was at Manchester City proved to be the exception - they were a bit different, those matches always had an edge.
But when I was at Everton and Aston Villa, particularly at the peak of the Alex Ferguson era, the approach was to try and keep the score down when you were away to Manchester United - they were that good.
In fact, you didn't want to play that United side at home or away because they could simply pummel you.
They'd come at you from the left wing, right wing, through the middle, from set pieces. They could have a slow build-up or attack with speed. They had it all and when you tried to attack them, they'd do everything in their power - including fouls, if needed - to stop you from scoring.
That United side would put in a dirty tackle, commit a professional foul, to stop us getting something against them, especially at Old Trafford. Now, I can't think of a single Premier League team who'd fear being thrashed at Old Trafford.
And I don't see anything close to that desire in the current United side that would make me, as an opposing player, fear them.
Teams now would fear Liverpool and Manchester City, just for the way they play. They dominate you, they push you back, grind you down, smother you with pressure.
But not United. They can score goals, put a nice move together but they will also give any team a chance in a game.When United press now, they don't do it with intensity, so any team that plays them know they'll have the opportunity to attack.
I watched the United versus Southampton game last weekend and what struck me was their lack of speed in passing the ball. Harry Maguire will get the ball, roll it out to the left back; he'll roll it into midfield; the midfielder will roll it up to one of the forwards. I watch Liverpool and Manchester City - Chelsea as well - and the ball just moves so much faster, they fire passes into team-mates which creates the tempo for the game. I don't see that tempo with United
That fear factor is long gone, more evidence of that this week with United's defeat at home to PSG.
This United side is certainly not capable of winning the Champions League and they'll struggle to even compete in the Premier League, that's a distant objective for them now as they are just too inconsistent.
It's impossible to have confidence in United putting a run together.
Presuming that Ole Gunnar Solskjaer's team go through to the knockout stages of the Champions League, most of the other teams in the competition would fancy playing them in the next round - and that's a terrible indictment.
United have one big result in them but it's more difficult to do that over two legs in Europe.
It's difficult to put your finger on what's wrong at Old Trafford. They have some really good players, they win some games where you think, that's it, they have turned a corner now, but suddenly they just drop off and it's back to where they were.
Whether that's down to the manager or the players' attitude, I don't know.
United started the week knowing they needed one point from the last two games in the group to get into the knockout stage… now they need to go to Germany and get something in Leipzig.
Istanbul is where it all went wrong for United in Europe this season. The games with PSG and Leipzig were always going to be tricky but they started well, beating PSG in Paris and thrashing Leipzig 5-0 at Old Trafford.
They had done the hard bit and Istanbul away was their chance to make progress a lot easier, but the 2-1 defeat in Turkey was a big letdown and now they are paying a very high price for that failure.
I'd still expect United to go through, they play well away from home. They seem to like it when teams come at them and attack them, so they can counter-attack - and they have picked up some good wins that way. The way the next game is set up, Leipzig having to win, suits United, they can play on the break.
So they should make it out of the group but it's a far from ideal situation, with a tough away game in Germany to qualify. It should have been put to bed before this and it just sums up the inconsistency that haunts Manchester United.
Solskjaer should have taken Fred off at half-time in that PSG game as he was already on a yellow card.
You need your manager to make decisions at the right time, but Solskjaer just carried on in hope. He should have been cuter.
United have West Ham this weekend, which is a big game for former Old Trafford boss David Moyes. The Scot is creating a proper team there - they are very dogged, winning games by the odd goal.
The Hammers flirted with relegation earlier but now they look like a solid top-half side, they will be awkward for most teams to play against but especially for United at the moment.