If the team isn't built around Eden Hazard, he will not be world-class, as evident with his performances for Belgium under Georges Leekens.
Keep in mind, Hazard didn't like Leekens and Leekens didn't like Hazard.
Here's a quote from Marc Wilmots, the new Belgian manager, and make sure you read between the lines: "He's always wanted to wear the number 10 shirt and he will get it. No one is bigger than the team but I'm planning to give a special role to Eden."
Hazard loves the attention; he wants to be courted, so he needs to be treated well. When he found out Real Madrid didn't want him, he stopped flirting with them.
For a player so lethal out wide, he doesn't want to play there anymore:
It is all down to that. I have always dreamed of playing the number 10 role, and wearing that number on my back, and you can see what a difference it makes from how many goals I have scored and set up for others. That will be a consideration when I decide on my club. Where I will play will influence my thinking on who I should join.
This season, he has a goals scored/created average of 0.90 per game when he plays as an attacking midfielder.
Read the bolded part of his quote, and let's look at the three teams in the running for his signature.
Chelsea (4-2-3-1): Potentially, Chelsea could play Hazard, Ramires and Juan Mata as the three attacking midfielders in the 3 of the 4-2-3-1. Ideally, it's three interchangeable attacking midfielders, but Hazard and Mata will do the interchanging.
Manchester City (4-4-2): They don't play an attacking midfielder. David Silva and Samir Nasri start out wide and drift centrally.
Manchester United (4-4-2): They don't play an attacking midfielder. They have two inside-out wingers in Ashley Young and Nani, whilst Antonio Valencia is a pure winger.
Chelsea are the only team with a designated attacking midfielder.
City are more flexible, so they can change to a 4-2-3-1, whereas the 4-4-2 is ingrained in Sir Alex Ferguson.
It's one thing playing as a wide forward in a 4-3-3; it's another to play as a winger in a 4-4-2, where you have to attack and defend. With 0.7 tackles and interceptions per game, Hazard doesn't want to defend.
Statistics courtesy of WhoScored.com.
Please read Gregory Van Der Wiel Would Be a Stupid Signing.