Over the years, Manchester United have had some brilliant full-backs down the years who have been reliable, superb servants for the club. A full-back, particularly for Manchester United, has been vital for the club over the years as they have provided an extra layer in attack which have been vital for the club over the years. Here, we will rank the top five left-backs of all time who have played for United which is brought to you by United In Focus. 5 – Roger ByrneStarting our list is consistent defender Roger Byrne, who was awarded the United captaincy in the 1955/56 season. Byrne made his de…