When a firm appoints a new manager, it reopens the possibility of new contractual friction with its partners. We explore strategic ambiguity as a potential for friction with a supplier. The firm’s new manager probably has fuzzy expectations about the supplier’s strategy. An optimistic manager weights favorable strategies more heavily than detrimental ones, whereas a pessimistic manager does the opposite. We show that the manager’s degree of optimism is critical: above a threshold, it can cause the supplier to change the timing of its contracting and increase its profits. We also find that this threshold degree of optimism depends on the degree of product substitution: it is more stringent with imperfect substitutes than with perfect substitutes or unrelated goods.