Wordpress - add custom rewrite rule

functions.php

<?php

// Create the query var so that WP catches your custom /staff/username url
add_filter( 'query_vars', 'bb_rewrite_add_var' );
function bb_rewrite_add_var( $vars )
{
    $vars[] = 'staff';
    return $vars;
}

add_rewrite_tag( '%staff%', '([^&]+)' );
add_rewrite_rule(
    '^staff/([^/]*)/?',
    'index.php?staff=$matches[1]',
    'top'
);

add_action( 'template_redirect', 'bb_rewrite_catch' );
function bb_rewrite_catch()
{
    global $wp_query;

    if ( array_key_exists( 'staff', $wp_query->query_vars ) ) {
        include (TEMPLATEPATH . '/user-profile.php');
        exit;
    }
}