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West Ham will demand at least £6.5million for Matthew Upson should he be sold this summer.

The England centre half has yet to play a full game since signing from Birmingham in January and he is ruled out of Saturday's derby at Arsenal with a calf problem.

It is understood that, although Upson and full back Lucas Neill, signed from Blackburn for £1.5m, have clauses in their contracts allowing them to leave if West Ham are relegated, it is stipulated that the club will not take a loss on their January transfer fees.

Manager Alan Curbishley said: "As I understand it, West Ham are under no pressure to let these players go unless certain figures are matched. I'm under no pressure, if the worst comes to the worst, to let anyone go. We're concentrating on what remains of this season, starting with Arsenal, rather than anything else."

West Ham have a daunting run-in, with games against Chelsea and Manchester United still to come.

But Curbishley, likely to stick with the side that beat Middlesbrough, said: "I know we have some difficult games ahead but we need to win at least four of the last seven, and I think we can."

Meanwhile, Emmanuel Adebayor, who is set to lead the Arsenal attack, has vowed to become Africa's best footballer within three years.

The 22-year-old striker hopes to one day be mentioned in the same breath as Samuel Eto'o and African footballer of the year Didier Drogba.

Adebayor said: "I'm getting better and better. I have plenty of time to win African Footballer of the Year. I have been second once and third once, so I believe I can win it in the next two or three years. I am learning a lot at Arsenal. It would be great to be one of the best in the world one day. That is why I am working hard. For me, the important thing is to be consistent. In every game I have to show I am a good player."

Arsenal expect to have Gilberto Silva back in midfield after he missed the Liverpool defeat through injury.