Suppose the initial chain is Ahmad ← Malik ← Nafi‘ ← Ibn ‘Umar, while another is ‘Ali ← ‘Ubayd Allah ← Nafi‘ ← Ibn ‘Umar. The new route does not transmit directly from Malik; it meets the first route at Nafi‘.
This is a partial mutaba‘ah (qasira). Its convergence lies higher in the chain, above the narrator's immediate teacher. It may still corroborate the substance of the report through another path to the same Companion.
Even when agreement is only found further upward, near the Companion, the key point remains: the supporting route does not share the initially investigated teacher.