TableSort & orderByHeader: How to specify default sort column?

Is there any way, when creating a sortable table, that I can specify which field the table should initially be sorted on? I can easily do it like this:

$query->orderBy('efficiency', 'desc');

However if I am making a sortable table (by adding clickable headers) I have to order it like this:

  $query = $query
                ->extend('TableSort')
                ->orderByHeader($header_row);  

And it default sorts on the first table column, which is not how I want my table to sort by default. Also, I would love to be able to set the default direction of sorting per column, but this seems to be impossible.

Here is all my code:

  $table_rows = array();
  
  $header_row = array(
    array('data' => 'Player', 'field' => 's.last_name'),
    array('data' => 'Team', 'field' => 's.team_id'),
    array('data' => 'Pos', 'field' => 's.position'),
    array('data' => 'MP', 'field' => 's.minutes'),
    array('data' => 'Pts', 'field' => 's.points'),
    array('data' => 'Reb', 'field' => 's.rebounds'),
    array('data' => 'Ast', 'field' => 's.ast'),
    array('data' => 'Stl', 'field' => 's.stl'),
    array('data' => 'Blk', 'field' => 's.blk'),
    array('data' => 'TO', 'field' => 's.tov'),
    array('data' => 'PF', 'field' => 's.pf'),
    array('data' => 'Eff', 'field' => 'efficiency',  'sort' => 'DESC'),    
  );
  
  $query = db_select('nba_stats_daily', 's');
  $query->condition('s.game_date', $date_text, '=');
  $query->fields('s', array('name', 'team_id', 'position', 'minutes', 'points', 'rebounds', 'ast', 'stl', 'blk', 'tov', 'pf', 'efficiency')); 
  $query = $query
                ->extend('TableSort')
                ->orderByHeader($header_row);                
  $result = $query->execute();
  
  foreach($result as $stat_line) {
    
    $table_rows[] = array(
      array('data' => $stat_line->name),
      array('data' => $stat_line->team_id),
      array('data' => $stat_line->position),
      array('data' => $stat_line->minutes),
      array('data' => $stat_line->points),
      array('data' => $stat_line->rebounds),
      array('data' => $stat_line->ast),
      array('data' => $stat_line->stl),
      array('data' => $stat_line->blk),
      array('data' => $stat_line->tov),
      array('data' => $stat_line->pf),
      array('data' => $stat_line->efficiency),
    );
         
  }
  
  //return a themed schedule table
  return theme_table(array('header' => $header_row,
                           'rows' => $table_rows,
                           'attributes' => array('class' => 'table_dfs', 'width' => '100%'),
                           'caption' => '',
                           'colgroups' => array(),
                           'sticky' => FALSE,
                           'empty' => 'No data is available',
                          ));  

In the example above, when the table is initially rendered it sorts on the Player field. I want it to sort on Efficiency by default. Am I doing something wrong? This seems to be a lot more confusing than the documentation had me first believe.

Thanks!