  In soccer, passing is the most frequent interaction between players and plays
a significant role in creating scoring chances. Experts are interested in
analyzing players' passing behavior to learn passing tactics, i.e., how players
build up an attack with passing. Various approaches have been proposed to
facilitate the analysis of passing tactics. However, the dynamic changes of a
team's employed tactics over a match have not been comprehensively
investigated. To address the problem, we closely collaborate with domain
experts and characterize requirements to analyze the dynamic changes of a
team's passing tactics. To characterize the passing tactic employed for each
attack, we propose a topic-based approach that provides a high-level
abstraction of complex passing behaviors. Based on the model, we propose a
glyph-based design to reveal the multi-variate information of passing tactics
within different phases of attacks, including player identity, spatial context,
and formation. We further design and develop PassVizor, a visual analytics
system, to support the comprehensive analysis of passing dynamics. With the
system, users can detect the changing patterns of passing tactics and examine
the detailed passing process for evaluating passing tactics. We invite experts
to conduct analysis with PassVizor and demonstrate the usability of the system
through an expert interview.
