Finally I did it using asp for the second dropdownlist:
<asp:DropDownList ID="DropDownListRepIns" runat="server" AppendDataBoundItems="True" EnableViewState="false"
DataSourceID="SqlDataSourceGetPlayers"
DataTextField="HOME_PLAYER_S" DataValueField="HP_ID" >
<asp:ListItem Text="ΠΑΡΑΚΑΛΩ ΕΠΙΛΕΞΤΕ ΑΓΩΝΑ" Value="0" />
</asp:DropDownList><br />
and a c# code for event item inserting that binds manually:
protected void FormViewReport_ItemInserting(object sender, FormViewInsertEventArgs e)
{
e.Values["HOME_PLAYER_ID"] = ((DropDownList)((FormView)sender).FindControl("DropDownListRepIns")).SelectedValue;}
Also the solution this solution works without needing code behind:
SelectedValue='<%# DataBinder.Eval (Container.DataItem, "HOME_PLAYER_ID") %>'
You have to use this in the second dropdownlist in asp.