Bulgarian Dimitar Berbatov is the leading goalscorer in the Barclays Premier League and Edin Dzeko, a Bosnian, will hope to come off the bench and have an impact to justify his ?27million price-tag.
'One of the best strikers in the world': Berbatov
But life has not always been about expensive transfers and bulging wage packets. Alex Kay spoke to some of the people who know them best.
Kiril Stoikov, a former team-mate at FC Pirin, Berbatov's first club
He started coming to the ground aged six to watch his father, Ivan - a centre half. Once Dimitar started playing, he was unique because he always played with the older groups. This may be why he's become so excellent as a striker.
Dimitar was a pleasure to be around, but I remember when he was playing for CSKA Sofia and came back to Blagoevgrad to see his former team-mates play. He got so frustrated with a linesman's decision he threw a bunch of branches at him. A policeman screamed at him to stop.
Juande Ramos, his coach at Tottenham
You have to accept that you have someone who is technically brilliant but who is not going to be scrapping for every loose ball. He trained very much at his own pace. He programmed himself to be right for match days but you accept that because you know he will then go out and get you three points. He needs to be loved. But I completely understood that he had a fantastic opportunity (at United) and he wanted to take it.
Bulgaria legend, Hristo Stoichkov
Sometimes it seems as though his mind is not on the pitch; that he's somewhere else but that could not be further from the truth. He is deeper into the game than most other players but it shows itself in different ways.
I've seen every game he has played this season and no-one should doubt his desire. People question him, and then he scores three against Liverpool and he is everyone's favourite again. I can assure United fans they never need to doubt his commitment and as he starts getting their affection then he will just get better and better. He's one of the best players in the world and has been for a long time.
Mirza Trbonja, Dzeko's schoolmate
'United should be scared of him': Dzeko
I went to high school with him for four years. He is the same size now as he was then - very tall and quite skinny. He was of course obsessed by football and talked about it and watched all the time - it was his life.
He was a good student, particularly at maths and English and also played basketball and was very good. He liked to watch handball too and still goes to games when he is back. His sporting brilliance meant he almost always had a girlfriend - they were always flocking round him because he was a footballer.
Amar Osmin, coach at his first club Zeljeznicar
I have known him since he was eight, when he started training with the youth team just after the war. He scored so many goals - one season he managed more than 50. He knew when to shoot powerfully, dink it, use a lob. He came from a normal family - not so rich, not so poor, his dad drove a cab.
People at Zeljeznicar still talk about him, even though he was only in the first team for a couple of years. They follow every City game. United should be scared of him.
Marcel Schafer, his skipper at Wolfsburg
It was always inevitable Edin would move on, because he is such a good player, but he was also valued as a person here. You might expect someone in his position to forget quickly about Wolfsburg and concentrate only on his new club, but that was never likely to happen with him.
My mobile phone beeped the other day, and it was a text from Edin, wanting to know what had gone wrong. He had heard about all our injuries and wanted to know how serious they were and when each player would be back. That shows how much he still cares about us all at Wolfsburg, and I'm not surprised, because he was a friend as well as team-mate. You can always separate someone's professional ambition from how they are as an individual. In Edin's case, he was outstanding on the pitch, really important for us, and a great human being off it.
P.S United should know all about the dangers of Dzeko. He scored twice against them for Wolfsburg, including an impressive towering header at Old Trafford in the Champions League last season.
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Explore more:People: Edin Dzeko, Dimitar Berbatov, Juande Ramos Places: Liverpool, Manchester, Bulgaria