A central function of organizational boundaries is to help people know what they are to do with whom and how, which enables them to work together. Sustained product innovation in very large organizations requires that perhaps thousands of people across the organization know how to join up, participate in, and move in and out of many new product teams, so a boundary that can keep all these roles and relationships sensible is especially important for innovation. Using grounded theory building, we find that a boundary of team play enabled heedful interrelating and thus the easy formation of multiple teams over time in the large organizations we studied, while a boundary of detachment thwarted organization-wide innovation. Play embodies open, improvised, fluid and energized relations, while team play reflects the emergent yet dynamic space of heedful interrelating. Our study details how team play vs. detachment enable or disable innovation teams, and suggests how managers can implement or maintain the heedful social relations that are necessary for sustained innovation.