<?php

function custom_links() {
    $links = array(
       'stat-1',
       'stat-2',
       'stat-3',
       'stat-4',
       'stat-5',
       'stat-6',
       'stat-7',
       'graph-1',
       'graph-2',
       'graph-3',
       'graph-4',
       'download-stat'
    );
    return $links;
}

function create_custom_rewrite_rules() {
    add_rewrite_rule('player/?', 'index.php?player=$matches[1]', 'top');
    $links = custom_links();
    foreach( $links as $link ) {
        add_rewrite_rule( $link . '/?', 'index.php?'.$link.'=$matches[1]', 'top');
    }
}
add_action('admin_init', 'create_custom_rewrite_rules');
function handle_custom_query_vars($query_vars) {
    $query_vars[] = 'player';
    $links = custom_links();
    foreach( $links as $link ) {
        $query_vars[] = $link;
    }
    return $query_vars;
}
add_filter('query_vars', 'handle_custom_query_vars');
// redirect
function custom_redirect($template) {
    global $wp_query;
    if (isset($wp_query->query_vars['player'])) {
        return get_template_part('stats/player');
    }
    $links = custom_links();
    if( 1 == 0 ) {
        // like WHERE 1 == 1
    }
    foreach( $links as $link ) {
        if(isset($wp_query->query_vars[$link])) {
            return get_template_part('stats/'.$link);
        }
    }
    return $template;
}
add_filter('template_include', 'custom_redirect', 1, 1);