A club's approach to selling players should be that they'll do so when, and only when, it will improve the team. This changes with the club's overall position.
if you are a poor club with one very good player, then by selling that player you may be able to strenghten 3 or 4 other areas (for example, if blackpool or wolves had had carroll and decided to sell him). the team will be stronger even though none of the players may be as good as the one they replace.
when the team is reasonably strong but could use strengthening in limited areas, the process is harder to do with an overall benefit to the team but is still possible (villa selling carroll, for example).
when you are one of the best teams in the league, it is never wise to sell your best player (man u selling carroll, for example). you want the best player in the league in every position, if possible.
we are somewhere between the first and second examples. we shouldn't be in a hurry to sell, but shouldn't rule out the possibility either.
if you are a poor club with one very good player, then by selling that player you may be able to strenghten 3 or 4 other areas (for example, if blackpool or wolves had had carroll and decided to sell him). the team will be stronger even though none of the players may be as good as the one they replace.
when the team is reasonably strong but could use strengthening in limited areas, the process is harder to do with an overall benefit to the team but is still possible (villa selling carroll, for example).
when you are one of the best teams in the league, it is never wise to sell your best player (man u selling carroll, for example). you want the best player in the league in every position, if possible.
we are somewhere between the first and second examples. we shouldn't be in a hurry to sell, but shouldn't rule out the possibility either.