Please note: The master’s thesis presentation will take place online.
Miles Pitassi, Master’s candidate
David R. Cheriton School of Computer Science
Supervisor: Professor Tim Brecht
This thesis investigates two elements of hockey widely believed to be critical to success: puck possession and traffic (skaters who are in or near the triangular area formed between the puck and the posts during a shot attempt). Our analysis draws on puck and player tracking (PPT) data from the 2023–2024 and 2024–2025 NHL regular seasons. We determine average team puck possession percentage, defined as the average proportion of total game time that each team has possession of the puck. We find that this metric has only a moderate correlation with average goal differential (r=0.56). To further explore how different aspects of possession relate to team success, we compute additional metrics, including Average Offensive Zone Possession Time Differential (Avg. OZPTD). This captures the difference between the time a team spends with possession in the offensive zone and the time their opponents spend with possession in their offensive zone. We find a strong correlation (r=0.77) between Avg. OZPTD and average goal differential. Further analysis shows that Avg. OZPTD is stable across games, effectively distinguishes between teams, and, despite being correlated with existing metrics like Shot Attempt Percentage (SAT%), offers additional predictive value for goal differential. SAT% (also known as Corsi) refers to the percentage of total shot attempts that each team takes.
We also study the relationship between the amount of skaters creating traffic during shot attempts and shot outcomes. Our findings show that increased levels of traffic significantly increase the percentage of shot attempts that are blocked and reduce the chance of a shot attempt resulting in a shot on goal. Overall, we find that 29% of all shot attempts are blocked and that the highest goal rates occur from the center of the ice on short-to- mid-range attempts with no traffic present. For long-distance shot attempts that reach the goaltender, the probability of scoring increases with traffic. We also show that defensive skaters are primarily responsible for reducing shot-on-goal rates but can inadvertently increase goal likelihood on mid-range shot attempts (23-45 feet) presumably due to screening their own goaltender.
Together, the findings in this thesis offer valuable insights into how puck possession contributes to team success and how traffic influences shot outcomes. In addition to these empirical results, we contribute a suite of methodological techniques that can support future analysis of possession and traffic. We present a comprehensive pipeline for cleaning, filtering, and processing individual possession data sourced from the NHL’s puck and player tracking system which is an essential foundation for our findings and a resource for future research. We also describe how we assemble a set of shot events by aligning official NHL API shot data with shot attempts in the PPT data. This involves adapting the NHL’s own inference algorithms to identify undetected shot attempts and applying custom techniques to improve timestamp accuracy.