Understanding how individuals monitor and adapt to errors in social contexts, particularly in team sports, is crucial for optimizing performance. Despite a substantial literature on (social) error monitoring, the social error monitoring processes of athletes have received little attention. This research proposal outlines a stepwise exploration of athletes' post-error responses to errors by teammates vs. opponents in basketball and American football. The proposal integrates analyses of real-game data with controlled lab studies, including EEG and facial EMG measurements, to investigate the behavioural, affective and neurophysiological responses to errors by teammates vs. opponents. The overarching objective is to investigate whether the affective-signalling hypothesis, until now only applied to individual error monitoring, can be extended to the context of team sports and synthesized with hypotheses derived from the goal representation hypothesis on social error monitoring. By shedding light on how athletes respond to errors in different social relationship, our research not only contributes to theories on social error monitoring but also holds significant relevance for the field of sport psychology.