The Champions League and Premier League have much in common; cauldron-like atmospheres, intense, fast-paced football, and buckets of controversy.
But former top referee Graham Poll, who has overseen some of the biggest games in England and Europe in recent years, can spot one major difference.
"Players are better behaved in the Champions League than they are in the Premier League - without a doubt," said Poll.
Widely thought to be one of the most authoritative referees of his generation, and a veteran of 329 Premier League matches and 43 Champions League games, he is well placed to judge.
With the quarter-finals the prize in this week's Champions League second legs, Poll gives BBC Sport his insight into refereeing matches at home and abroad.
WHAT'S IT LIKE TO REF IN THE PREMIER LEAGUE?
You can understand the pressures that are coming from Arsenal at the moment, wanting to give protection to their players. And you'll get Sir Alex Ferguson putting pressure on because he wants to win the title.
That sort of thing builds.
Whether consciously or subconsciously, that affects how refs approach what happens on the pitch. It's bound to.
When you've got a big game coming up - say Arsenal versus Man United - there's big build-up in the press and television are doing great big things about the pressure being on, it's an unrefereeable match, etc.
And that pressure is obviously going to affect referees.
Some read newspapers; some try to avoid them completely. But it's going to affect you.
Along with the pressure that builds up on you through the media, you've got familiarity breeding contempt - players see the same referees all the time. They already have an [often negative] impression of them.
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If you're refereeing in the Premier League week-in week-out you're being battered by the press on a very regular basis.
WHAT'S IT LIKE TO REF IN THE CHAMPIONS LEAGUE?
If you're appointed to go out and referee AC Milan versus Real Madrid, you fly into the country the day before, you can't speak Italian, and so you can't read the newspapers.
Consequently you don't get any of the pressure involved in it, you referee the game, have a meal afterwards, and fly home.
It is a completely different feel and different pressure involved.
Additionally, if you go out to Milan and the game doesn't go so well, you probably won't go back there for four years.
And referees are treated much, much better off-the-field abroad than they are here.
The Champions League is officiated by the top 30 referees in Europe.
Howard Webb - our number one referee - hasn't had controversy all season in 24 Premier League games. No problems. He is of the standard that referee in the Champions League every week.
You have got the best referees doing the best matches - and that's how it should be.
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For a start, the referee is not affected by the continual pressure within that country.
"In very few jobs do you have 60,000 people, plus millions more via television cameras from every angle, watching your every single move like a ravenous hawk"
CW
WHY ARE PLAYERS BETTER BEHAVED IN EUROPE?
Pierluigi Collina said to me that what makes a good referee is "when the players accept your mistakes and still think you're a good referee".
That's the difference.
When someone such as new Premier League Lee Mason, for example, goes and referees Liverpool the players are looking at him and don't know how he will react.
And when he makes a mistake, they think he's a bad referee.
When I was doing it I'd make a mistake and Steven Gerrard would say "never mind, Polly" and you get on with it. He still thinks you're a good ref.
Even the press, who might not like your style, will accept it. You are labelled a good referee who had a bad match.
That is a key difference. Every referee in the Champions League is recognised as a good referee.
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They are more respectful because they recognise that they are being refereed by one of the elite referees within Europe and they respect that.
(200 games so far):
(2.61 per game)
(one every 16.7 games)
(554 games so far):
(1.67 per game)
(one every 12.3 games)
WHAT'S THE SECRET TO BECOMING A TOP EUROPEAN REFEREE?
You won't see Howard Webb walking backwards and running away from players now. Because he's got the confidence to know he's one of the top referees in Europe which means he can stand up to the players.
With players, it's that animalistic instinct.
If they think there is fear, they march forward and you go back because you're scared and that encourages them.
When they sense that inner confidence, they don't even try it on.
Some refs have got it and some haven't
With the infamous Andy D'Urso incident [when Manchester United played Middlesbrough in January 2000], Roy Keane said he couldn't have done it to me.
Those that have that get to the top of the tree in refereeing - and they don't get chased around a football pitch.
There's some very fine moments for referees such as the dignity Collina showed in the Nou Camp in 1999 when he helped the Bayern players up who were completely shattered having conceded those two goals to Man United.
In the refereeing world there's a video which shows those final minutes with a camera trained on Pierluigi showing how brilliant he was in those moments.
It's just an example of highlighting something which a referee does very well, rather than always highlighting errors and mistakes.
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It comes from inner confidence.
MOST HOSTILE CHAMPIONS LEAGUE ATMOSPHERE?
I refereed all three teams there - Fenerbahce, Galatasaray, and Besiktas - and actually sent Jaap Stam off there once.
With the intensity and the fervour of the crowd, anyone that refereed there will be moved by it. Not affected and giving decisions, just moved.
The intensity - not just at the game - but right across the city throughout the whole day, is an unbelievable feeling. Everyone is on about that game.
Football is such a passion for the Turks. It's certainly the most intimidating atmosphere.
Some people ignore it and close it out; some people embrace it.
I used to love the big occasions and take it all in and on board - it used to motivate me and drive me on. The bigger the place, the bigger the challenge.
When you step up to that level in one of those huge places - I did a Real Madrid Champions League semi-final at Bayern Munich - if you can't do it, you should not be out there.
You've got a perfect playing surface, a huge passionate crowd, 22 brilliant players - what more do you want?
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Istanbul is the most intense atmosphere.
HOW CAN THE REFEREEING SITUATION BE IMPROVED?
But it's too easy to have a go at refs all the time. You know they won't bite back and that they'll just get on with it.
Sitting there with a bank of video monitors, replaying the incident and watching it back over and over again, is very easy.
Referees do a very good job for a fraction of the money players get.
The reason referees make mistakes is due to pressure. Pressure makes you do strange things which you cannot always explain.
The best thing people can do is to encourage referees and be positive about them - and you will see their performances improve as a result.
If what you want is good refereeing, which helps the football match, then you should look at that and embrace it.
Let's encourage referees and be positive - rather than sniping at them and always being negative and slating them.
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Football is about footballers, not referees.
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