Use call within call

<ul>
<?php
$args = array( 'numberposts' => 5, 'post_type' => 'post', 'tag' => '<?php echo $post->post_name; ?>', 'field' => 'slug' );
$rand_posts = get_posts( $args );
foreach( $rand_posts as $post ) : ?>
	<li><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></li>
<?php endforeach; ?>
</ul>

This works when I enter a tag in the ‘tag’ field but I can’t get it to work when it uses the tag as the post name. I have a custom post type where there is a tag with the same slug for each post. So how can I get this call to work?