AI 中文总结
该研究提出用于足球转播的无球控球质量指数，通过两个层面区分创造空间的有效控球与无效控球，补充了现有有球价值框架的不足，相关指数与比赛积分、预期进球差显著相关。
AI 中文摘要
控球是足球中被引用最多也最具误导性的数据：在己方半场完成的60%的控球，并非意味着用60%的控球将对手压制在后方。现有的基于事件的控球价值框架（预期威胁、VAEP、有球价值）仅对有球动作定价，却忽略了无效控球带来的无球问题：控球是创造了空间，还是陷入了无效循环？我们从两个层面回答这一问题。首先，事件端的无效控球指数通过预期威胁网格下的峰值威胁增益对每个控球序列定价，在重建实时比分以排除为保住领先优势的控球循环后，标记出平局或落后状态下的低威胁序列。在2026年FIFA世界杯（103场比赛，206场球队比赛）上，该标记与积分呈负相关（r=-0.37），与预期进球差呈负相关（r=-0.51，部分与指数耦合）。它并非有球价值的重新包装：在控制球队进攻VAEP和场地倾斜度的情况下，无效标记仍与积分呈显著负相关（p<0.0001，且按比赛聚类），而VAEP在此类同场（描述性）回归中不显著——该指数在有球动作价值模型之外提供了额外信息。其次，针对被标记的窗口，我们将转播视频投影到球场坐标，通过测量创造空间指数（SCI）来判断其是空间无效还是空间创造：这是一种净场地控制变化，用于判断控球是夺取了空间还是将对手防线向后推。在9场世界杯比赛的35个被标记窗口中（目的性抽样），74%为空间非创造型，19%为弱推进型，6%为空间创造型窗口——仅事件标记会将其判定为失败，其中包括一支控球率达73%却以点球大战出局的球队（两个非创造型窗口）。这两个层面区分了创造空间但未转化与无效控球，这是仅基于事件的有球价值无法做到的区分。
英文摘要
Ball possession is the most-cited and most-misleading number in football: 60% recycled in one's own half is not 60% spent pinning the opponent back. Existing event-based possession-value frameworks (expected threat, VAEP, on-ball value) price on-ball actions but ignore the off-ball question a sterile possession poses: did holding the ball create space, or was the circulation dead? We answer this in two layers. First, an event-side junk-possession index prices each possession sequence by its peak threat gain under an expected-threat grid and -- after reconstructing the live scoreline to exclude lead-protecting circulation -- flags low-threat sequences in tied-or-losing states. On the 2026 FIFA World Cup (103 matches, 206 team-matches) the flag correlates negatively with points (r=-0.37) and xG difference (r=-0.51, partly index-coupled). It is not a repackaging of on-ball value: with team offensive VAEP and field tilt held fixed, the junk flag stays strongly negatively associated with points (p<0.0001, also match-clustered) while VAEP is not significant -- in this same-match (descriptive) regression it adds information beyond this on-ball action-value model. Second, for a flagged window we resolve whether it was spatially dead or space-creating by projecting broadcast video to pitch coordinates and measuring a Space-Creation Index (SCI): a net pitch-control change capturing whether the possession seized space or pushed the opponent's block back. Across 31 of 35 flagged windows from nine World Cup matches (a purposive sample), 74% are spatially non-space-creating, 19% weak progression, and 6% space-creating windows the event flag alone would score as failure -- including a side with 73% of the ball that exited on penalties (two non-creating windows). The two layers separate space-creating-but-unconverted from sterile possession, a distinction event-only on-ball value cannot make.
Comments11 pages, 2 figures. Code and data pipeline: https://github.com/nowayfootball/junk-possession
