WP REST API Controller Update Items

<?php
class Sports_Bench_Team_REST_Controller extends WP_REST_Controller {
  /**
	 * Update one item from the collection
	 *
	 * @param WP_REST_Request $request Full data about the request.
	 * @return WP_Error|WP_REST_Response
	 */
	public function update_item( $request ) {
		$item = $this->prepare_item_for_database( $request );

		if ( function_exists( 'sports_bench_rest_update_team')  ) {
			$data = sports_bench_rest_update_team( $item );
			if ( is_array( $data ) ) {
				return new WP_REST_Response( $data, 200 );
			} else {
				return $data;
			}
		}

		return new WP_Error( 'cant-update', __( 'message', 'text-domain'), array( 'status' => 500 ) );

	}
}

function sports_bench_rest_update_team( $item ) {
	global $wpdb;
	$table_name = $wpdb->prefix . 'sb_teams';

	$team_id = $item[ 'team_id' ];
	$slug_test = $wpdb->get_results( "SELECT * FROM $table_name WHERE team_id = $team_id" );

	if ( is_array( $slug_test ) ) {
		$result = $wpdb->update( $table_name, $item, array ( 'team_id' => $item[ 'team_id' ] ) );
		if ( $result ) {
			return $item;
		} else {
			return new WP_Error( 'error_team_update', __( 'There was an error updating the team. Please check your data and try again.', 'sports-bench' ), array ( 'status' => 500 ) );
		}
	} else {
		return new WP_Error( 'error_team_update', __( 'This team does not exist. Try adding the team first.', 'sports-bench' ), array ( 'status' => 500 ) );
	}
}
?>