Change blog single page permalink

Use The below code in functions.php in current active theme to change the blog single page permalink.

<?php
function filter_post_link($permalink, $post) {
	if ($post->post_type != 'post')
		return $permalink;
	return 'blog'.$permalink;
}
add_filter('pre_post_link', 'filter_post_link', 10, 2);


add_action( 'generate_rewrite_rules', 'add_blog_rewrites' );
function add_blog_rewrites( $wp_rewrite ) {
	$wp_rewrite->rules = array(
		'blog/([^/]+)/?$' => 'index.php?name=$matches[1]',
		'blog/[^/]+/attachment/([^/]+)/?$' => 'index.php?attachment=$matches[1]',
		'blog/[^/]+/attachment/([^/]+)/trackback/?$' => 'index.php?attachment=$matches[1]&tb=1',
		'blog/[^/]+/attachment/([^/]+)/feed/(feed|rdf|rss|rss2|atom)/?$' => 'index.php?attachment=$matches[1]&feed=$matches[2]',
		'blog/[^/]+/attachment/([^/]+)/(feed|rdf|rss|rss2|atom)/?$' => 'index.php?attachment=$matches[1]&feed=$matches[2]',
		'blog/[^/]+/attachment/([^/]+)/comment-page-([0-9]{1,})/?$' => 'index.php?attachment=$matches[1]&cpage=$matches[2]',
		'blog/([^/]+)/trackback/?$' => 'index.php?name=$matches[1]&tb=1',
		'blog/([^/]+)/feed/(feed|rdf|rss|rss2|atom)/?$' => 'index.php?name=$matches[1]&feed=$matches[2]',
		'blog/([^/]+)/(feed|rdf|rss|rss2|atom)/?$' => 'index.php?name=$matches[1]&feed=$matches[2]',
		'blog/([^/]+)/page/?([0-9]{1,})/?$' => 'index.php?name=$matches[1]&paged=$matches[2]',
		'blog/([^/]+)/comment-page-([0-9]{1,})/?$' => 'index.php?name=$matches[1]&cpage=$matches[2]',
		'blog/([^/]+)(/[0-9]+)?/?$' => 'index.php?name=$matches[1]&page=$matches[2]',
		'blog/[^/]+/([^/]+)/?$' => 'index.php?attachment=$matches[1]',
		'blog/[^/]+/([^/]+)/trackback/?$' => 'index.php?attachment=$matches[1]&tb=1',
		'blog/[^/]+/([^/]+)/feed/(feed|rdf|rss|rss2|atom)/?$' => 'index.php?attachment=$matches[1]&feed=$matches[2]',
		'blog/[^/]+/([^/]+)/(feed|rdf|rss|rss2|atom)/?$' => 'index.php?attachment=$matches[1]&feed=$matches[2]',
		'blog/[^/]+/([^/]+)/comment-page-([0-9]{1,})/?$' => 'index.php?attachment=$matches[1]&cpage=$matches[2]',
	) + $wp_rewrite->rules;
}
?>

After adding this code in functions.php please update your permalink.