How will Manchester United replace Cristiano Ronaldo?
Ronaldo will be sorely missed by United after his move to Real
It is the question that has provided the backdrop to their attempt to win a fourth successive Premier League crown - and I believe the answer is that they cannot replace him.
I think the fact that he is no longer at the club could be the difference between United winning and losing the title. He was that good and that important to them.
But I do not feel Sir Alex Ferguson had any option other than to sell Ronaldo.
If Ronaldo had wanted to stay, make no mistake United would have kept him. But he had been making noises about going for some time and there was almost an air of inevitability that he would leave Old Trafford.
The fee of £80m was astronomical and will have eased the pain of parting, but if you had offered Ferguson the choice of the cash or the player he would have kept Ronaldo every time - as long as the player had been happy to stay.
But he has gone and you return to that initial question about how to fill the gap he has left behind. And I just don't think you can.
There has never been a better player in the history of the Premier League at decimating what you might term "lesser" sides. History shows us that United's record in those kind of games was phenomenal.
When it came to the last 25 minutes when sides had been chasing the ball all day, they would understandably run out of steam and Ronaldo would just destroy them. He was fantastic at it because he seemed to get stronger - he annihilated those sides and earned United so many crucial wins.
People talked about him diving and having an ugly side to his game, but don't forget he was getting kicked and tackled all day long and just kept coming back for more.
He is a player with great feet, lightning pace, superb aerial ability, incredible strength and one could provide a stack of goals. I'd have a small bet that Liverpool and Chelsea's players were doing cartwheels when they heard he was being sold.
There is a psychological perspective to having a player as good as Ronaldo in your side and when opponents look at the team-sheet and see he is not there, they suddenly feel they have a better chance of winning.
Ferguson's vast experience will be crucial. He will be using all his expertise to think of systems and players he can utilise.
He will make sure they regroup and try to accentuate the positives. Ferguson will not be talking about Ronaldo - he will be focusing on the players he has got. Players come and go, but Ronaldo is a massive loss for United.
Wayne Rooney will play a more central - and influential - role now. This is his best position without a shadow of doubt, but it you ask any opposing team if they want to face United with Rooney and Ronaldo, or just Rooney, there will only be one response.
Rooney is a world-class player with a competitive edge and fantastic ability, but he has never hammered the lesser sides in the way Ronaldo did and United will miss that.
Owen can handle the pressure of playing for the champions
Antonio Valencia has arrived from Wigan, but he is a more orthodox wide man whereas Ronaldo played all across the attack and was devastating everywhere.
Of course the big surprise was the arrival of Michael Owen on a free transfer from Newcastle United.
You can be sure Ferguson has put together a shrewd package to bring him to Old Trafford and will be convinced he can restore Owen to near the top of the Premier League goalscoring charts.
Owen was born to score goals and being at a club like United will not worry him one iota - nor will wearing Ronaldo's old number seven shirt.
He has the self-confidence that tells him he belongs on the big stage, although it is fair to say he will never get another chance like this.
Owen has not played in a good club side for years so he will relish the prospect of being on the end of all the opportunities United will inevitably create, but there is another side to it.
It might have been better if he had signed at the start of last season, when Ronaldo was still there. He is coming into a team that has won three straight Premier League titles and been to two successive Champions League finals; if they start to struggle he may have the finger pointed at him and find people saying "he ain't Ronaldo".
Michael's a big boy though and he can cope with the pressure. He has got a lot to prove at the age of 29 and he will realise that in some respects this is the Last Chance Saloon for him and will be intent on making the most of this move.
Benitez must put an end to Liverpool's habit of dropping points
I actually do not see United winning the title this year. Ronaldo just won too many games for them.
I believe that this will be Liverpool's year.
Draws at home against lesser teams cost Liverpool last season, but I think manager Rafael Benitez has learned how to play against them. Instead of waiting to see what they will do, he has gone for what Liverpool fans expect which is to try to hem these teams in and batter them.
It was a style of play that started when they thrashed Real Madrid 4-0 in the Champions League and continued from there. It was great to see, and I can see it bringing the title back to Anfield for the first time in 20 years this season.
Alan Hansen was talking to BBC Sport's Phil McNulty.
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