We analyse the spatial attendance spillover applying spatial panel-data models with the Italian Football League data from 2001/2002 to 2016/2017. Our Quasi-Maximum Likelihood empirical results suggest that no significant spatial interaction was evident in earlier seasons (2001–2013), but modest spatial spillover was in play from 2013 to 2016. In addition, cross-quality spillover exists only locally in the same cities. We use numerical simulations to examine the potential impact of such spillover on attendance distribution and then competitive balance; spillover implies an interaction between the two exclusive markets that are the principal sources of competitive imbalance. Our numerical simulations suggest that spatial spillover may create attendance variations across member teams. The final outcome depends on the spillover sign, the network structure, and the market size distribution. Combining the empirical results with numerical simulations, we find that a recent, slightly positive spillover may modestly reduce attendance disparity.