"We are not selling him. Rafael will have to live with it," sports director Dietmar Beiersdorfer said before Thursday's UEFA Cup qualifying match at Honved Budapest.
Van der Vaart wants to move to Valencia despite having a contract with Hamburg until 2010.
The Netherlands midfielder reported injured to the Hamburg squad for the match and is uncertain to play in Budapest. Van der Vaart said he had injured his back while lifting his one-year-old son.
German media have been skeptical of his explanation and have speculated that he is feigning injury so that he remains eligible to play in the Champions League for another club this season. If he plays in the UEFA Cup for Hamburg, Van der Vaart will not be able to play for another club this season in the Champions League.
Valencia is in Champions League qualifying.