Non-offloaded diabetic heel ulcers and the wound dressings used to treat them may be subjected to considerable bodyweight forces. A novel robotic foot phantom with a diabetic heel ulcer was designed and constructed to test the combined performances of applied primary and secondary dressings, in simulated non-offloaded (standing) and offloaded (supine) postures. We specifically compared the performances of the primary Exufiber dressing (Mölnlycke Health Care) combined with the secondary Mepilex Border Flex dressing (Mölnlycke) against a corresponding pair from an alternative manufacturer. Fluid retention and distribution between the primary and secondary dressings of each pair were determined using weight tests, and mechanical strength of the primary dressings was further measured postsimulated use through tensile testing. The Exufiber and Mepilex Border Flex pair performed similarly in the two simulated postures (retention = ~97%), whereas the comparator pair exhibited a 13%-decrease in retention for a supine to standing transition. Furthermore, the Exufiber dressing delivered up to 2-times more fluid to its paired secondary dressing and endured 1.7-times greater strain energy than the corresponding primary dressing before failure occurred. The present robotic foot phantom and associated methods are versatile and suitable for testing any dressing, in consideration of the relevant clinical factors and practice.