In his influential reading of Heroides 1, Duncan Kennedy argues that successful fictional letters can be felt to arise naturally from or be motivated by the depicted events and, ideally, be seen as agents in the forward movement of those events. Building on Kennedy's arguments, Peter Knox asserts that Ovid reconfigures his heroines in the Heroides to develop serious issues raised by his literary models from a new perspective. In this paper, I shall follow Kennedy's and Knox's suggestions to propose a new reading of Heroides 3. I shall first discuss how Briseis' letter can be felt to be both naturally motivated by and seriously engaged with Achilles' arguments in Iliad 9. More importantly, I shall argue that Ovid implicates Patroclus' aid in the composition and delivery of Heroides 3. The result is that one can view the fictional letter as having some influence upon Patroclus' fateful appeal to Achilles, thus providing an Ovidian reinterpretation of Iliad 16. Imagining this fictional role for Heroides 3 ultimately provokes comparison of Briseis, Patroclus and their relationships with Achilles. Such a reading uses Kennedy's and Knox's suggestions as a point of departure for making Heroides 3 a more successful and provocative fictional letter.