The Evolution of Expected Goals in Hockey Analytics

# The Evolution of Expected Goals in Hockey Analytics Expected Goals (xG) has become one of the most important metrics in modern hockey analytics. This article explores how the metric has evolved and transformed player evaluation in the NHL. ## The Origins of xG The concept of Expected Goals originated in soccer analytics before making its way to hockey. Early implementations were basic, considering only shot distance and angle. ## Modern xG Models Today's xG models incorporate numerous factors: - Shot distance and angle - Shot type (wrist, slap, backhand) - Rush shots vs. set plays - Rebounds and pre-shot movement - Screens and traffic in front of the net - Game state (even strength, power play) ## Impact on Player Evaluation xG has revolutionized how we evaluate both shooters and goaltenders: ### For Shooters Players who consistently outperform their xG are considered elite finishers with above-average shooting talent. ### For Goaltenders Goals Saved Above Expected (GSAx) has become the gold standard for evaluating goaltender performance. ## The Future of xG As tracking technology improves, xG models will continue to evolve, incorporating: - Player tracking data - Puck tracking speed and trajectory - Defensive positioning - Goaltender positioning and movement The next generation of xG models will provide even more accurate predictions and insights into hockey performance.