The word upa when it means 'superior' or 'inferior to' is karma-pravacanīya,
That is when the sense is that of 'over, above,' or 'inferior' as उपखार्यां द्रोणः a Drona is above a khari. उप निष्के कार्षापणः a karshapana is more than a Nishka. In this sense उप governs the Locative of the thing which is inferior 2.3.9. So also उप शाकटायनं वैयाकरणाः 'all grammarians are inferior to Sakatayana.' In this sense उप governs the accusative case.,