Ok, I understand.
So now I added this code
function _cm_getPkeyNames ($pkey_array, $task_id, $pattern_id=null)
// perform custom processing before the selection string is passed to another form.
{
$pkey_array[] = 'fecini'; // append to array
return $pkey_array;
} // _cm_getPkeyNames
to class team but the resulting sql in teamp_player_xref still hasn't the field fecini (allthough it's selected when accessing team).