Index: wp-admin/includes/ajax-actions.php
===================================================================
--- wp-admin/includes/ajax-actions.php	(revision 22961)
+++ wp-admin/includes/ajax-actions.php	(working copy)
@@ -1693,6 +1693,17 @@
 	wp_die( 0 );
 }
 
+function wp_ajax_preview_post_thumbnail() {
+	$post_id = intval( $_POST['post_id'] );
+	if ( ! current_user_can( 'edit_post', $post_id ) )
+		wp_send_json_error();
+
+	check_ajax_referer( 'preview_post_thumbnail-' . $post_id );
+
+	$thumbnail_id = intval( $_POST['thumbnail_id'] );
+	wp_send_json_success( _wp_post_thumbnail_html( $thumbnail_id, $post_id ) );
+}
+
 function wp_ajax_date_format() {
 	wp_die( date_i18n( sanitize_option( 'date_format', $_POST['date'] ) ) );
 }
Index: wp-admin/includes/post.php
===================================================================
--- wp-admin/includes/post.php	(revision 22961)
+++ wp-admin/includes/post.php	(working copy)
@@ -1120,8 +1120,8 @@
 	$post = get_post( $post );
 
 	$upload_iframe_src = esc_url( get_upload_iframe_src('image', $post->ID ) );
-	$set_thumbnail_link = '<p class="hide-if-no-js"><a title="' . esc_attr__( 'Set featured image' ) . '" href="%s" id="set-post-thumbnail" class="thickbox">%s</a></p>';
-	$content = sprintf( $set_thumbnail_link, $upload_iframe_src, esc_html__( 'Set featured image' ) );
+	$set_thumbnail_link = '<a class="choose button-secondary thickbox" href="%s">%s</a>';
+	$content = sprintf( $set_thumbnail_link, $upload_iframe_src, __( 'Choose a Featured Image' ) );
 
 	if ( $thumbnail_id && get_post( $thumbnail_id ) ) {
 		$old_content_width = $content_width;
@@ -1131,9 +1131,8 @@
 		else
 			$thumbnail_html = wp_get_attachment_image( $thumbnail_id, 'post-thumbnail' );
 		if ( !empty( $thumbnail_html ) ) {
-			$ajax_nonce = wp_create_nonce( 'set_post_thumbnail-' . $post->ID );
 			$content = sprintf( $set_thumbnail_link, $upload_iframe_src, $thumbnail_html );
-			$content .= '<p class="hide-if-no-js"><a href="#" id="remove-post-thumbnail" onclick="WPRemoveThumbnail(\'' . $ajax_nonce . '\');return false;">' . esc_html__( 'Remove featured image' ) . '</a></p>';
+			$content .= '<a href="#" class="remove">' . esc_html__( 'Remove featured image' ) . '</a>';
 		}
 		$content_width = $old_content_width;
 	}
Index: wp-admin/includes/meta-boxes.php
===================================================================
--- wp-admin/includes/meta-boxes.php	(revision 22962)
+++ wp-admin/includes/meta-boxes.php	(working copy)
@@ -1001,8 +1001,6 @@
  * @since 2.9.0
  */
 function post_thumbnail_meta_box( $post ) {
-	global $_wp_additional_image_sizes;
-
 	?><script type="text/javascript">
 	jQuery( function($) {
 		var $element     = $('#select-featured-image'),
@@ -1101,19 +1099,6 @@
 	</script>
 
 	<?php
-	$thumbnail_id   = get_post_meta( $post->ID, '_thumbnail_id', true );
-	$thumbnail_size = isset( $_wp_additional_image_sizes['post-thumbnail'] ) ? 'post-thumbnail' : 'medium';
-	$thumbnail_html = wp_get_attachment_image( $thumbnail_id, $thumbnail_size );
-
-	$classes = empty( $thumbnail_id ) ? '' : 'has-featured-image';
-
-	?><div id="select-featured-image"
-		class="<?php echo esc_attr( $classes ); ?>"
-		data-post-id="<?php echo esc_attr( $post->ID ); ?>">
-		<?php echo $thumbnail_html; ?>
-		<input type="hidden" name="thumbnail_id" value="<?php echo esc_attr( $thumbnail_id ); ?>" />
-		<a href="#" class="choose button-secondary"><?php _e( 'Choose a Featured Image' ); ?></a>
-		<a href="#" class="remove"><?php _e( 'Remove Featured Image' ); ?></a>
-	</div>
-	<?php
+	$thumbnail_id = get_post_meta( $post->ID, '_thumbnail_id', true );
+	echo _wp_post_thumbnail_html( $thumbnail_id, $post->ID );
 }
\ No newline at end of file
Index: wp-admin/admin-ajax.php
===================================================================
--- wp-admin/admin-ajax.php	(revision 22961)
+++ wp-admin/admin-ajax.php	(working copy)
@@ -56,7 +56,7 @@
 	'save-widget', 'set-post-thumbnail', 'date_format', 'time_format', 'wp-fullscreen-save-post',
 	'wp-remove-post-lock', 'dismiss-wp-pointer', 'upload-attachment', 'get-attachment',
 	'query-attachments', 'save-attachment', 'save-attachment-compat', 'send-link-to-editor',
-	'send-attachment-to-editor',
+	'send-attachment-to-editor', 'preview-post-thumbnail',
 );
 
 // Register core Ajax calls.