"Some time afterwards Longstreet also got himself damaged. A boot chafed his heel, which took on an ugly look and refused to heal. "Peter" (this was his West Point sobriquet, much used for him by his army friends and to this day not forgotten) therefore was obliged to don a slipper, and at Sharpsburg he was in no good humor at such footwear and the need of occasionally walking in it. In fact, a wobbly carpet slipper was not a good-looking thing for a commander in the field."
Source: Recollections of a Confederate Staff Officer
Commentary
The campaign following the decisive victory of 2nd Manassas was marked throughout by a series of odd events. An extremely superstitious person might have seen the warning signs. By the time of the final showdown at Sharpsburg, a series of unfortunate events had befallen the Army of Northern Virginia, the likes of which would make a probability statistician pull his hair from their roots.
The first of these was General Lee falling from a horse and injuring both hands, requiring him to be hauled around in an abulance for a period of time. "Stonewall" Jackson also was temporarily hurt. Longstreet was not immune, and the following recollection from Moxley Sorrel describes the somewhat comical events.