A 58-year-old man had a segment of superficial vein harvested from the right leg for a coronary bypass graft. The incision ran from just below the knee to the front of the medial malleolus. Six weeks later he describes numbness along the inner side of the right leg extending onto the medial border of the foot. Power throughout the right limb is normal, and sensation over the sole and the dorsum of the foot is unaltered.
Which one of the following nerves was most likely damaged during the vein harvest in this man's leg?