This study examines how teams respond to unplanned member loss. We draw on theory of team compilation and adaptation to suggest that teams with well-developed transactive memory systems (TMS) will be better equipped to withstand the loss of a member. Then, based on role criticality theories, we argue that those effects depend on which member is absent, such that when a more critical member is lost, the performance benefits of a TMS are reduced. Finally, we reason that this interactive effect is because of the team’s ability to engage in plan formulation. We tested and found support for our hypotheses using 78 four-member teams engaged in a command-and-control simulation. TMS positively affected team performance following the loss of a member, but the benefits of the TMS were reduced following the loss of a critical member because teams had more difficulty engaging in plan formulation. We discuss how the results of this study add to our understanding of the precursors of successful team adaptation.