Liverpool, Chelsea, Juventus and Manchester United have all been linked with Villa in recent months.
His agent, Jose Luis Tamargo, said: “He is waiting for an improvement of his contract.
“In England, they would pay Villa £4 million-a-year. Juventus would go up to £3.5 million-a-year.
“Valencia is a club with limited finances. It is no Real Madrid, nor Barcelona, nor Chelsea, nor Inter Milan. Valencia are very lucky to have such a player in their team.
“At the end of the season they will have to choose between whether they want to build a champion team with stars or listen to the offers that are going to arrive.”