You run a sports model (ELO ratings, the Massey method, or a machine-learning model) that outputs a win probability for each game, then trade whenever Polymarket's price differs from your model by more than a set threshold. The edge is having a calibrated probability the casual crowd lacks, applied across many games. Your model has to be good enough to beat the sharp sportsbook consensus, or the gap you're trading is just your own error.
Markets on Polymarket where sports analytics model is the natural play: