In the paper we provide the first formal definition of esports analytics and present a technique for automatically breaking up matches into encounters that permit detailed performance analysis. The technique is highly flexible and operational across a wide variety of contexts including physical sports. We use Multiplayer Online Battle Arena (MOBA) as a case as they are among the most played digital games in the world. In these games, teams of players fight against each other in enclosed arena environments, with a complex gameplay focused on tactical combat. The particular MOBA being examined in this paper, DOTA, already has millions of players. To win a match, a team has to develop its heroes by killing hostile units and buildings. This mostly happens during encounters involving players from both teams. Several encounters might occur simultaneously on different locations of the map. Thus, to evaluate game play, each fight has to be analyzed separately. We present a technique for segmenting matches into spatio-temporally defined components representing these encounters which enables us to analyze player performance on a detailed level. We apply encounter-based analysis to match data from the popular esport game DOTA, and present win probability predictions based on encounters. Finally, metrics for evaluating team performance during match runtime are proposed.