if he has another poor season, then he wont be worth any more than £5m.
Its a two way street. If spurs are no longer interested, then his best bet is signing a new deal with us with a min fee and working hard - he is a nailed on starter when fit and if he has an ok season, there will be renewed interest. If he goes somewhere a bit in-between - eg everton/ southampton - he might never play and that could damage his long term chances of getting the top level football he thinks he is good enough for.