In short
The answer first
A 'big chance' is a data-provider classification for an opportunity where a player would reasonably be expected to score. Opta describes examples such as one-on-one situations or very close-range chances with a clear path to goal and relatively limited pressure. It is an event label, not an official category in the Laws of the Game.
Key takeaways
Big chance is a provider-defined event classification rather than an IFAB rule.
Opta treats penalties as big chances under its event definitions.
The label identifies a high-quality opportunity but does not assign the same probability to every big chance.
A big-chance count and xG total measure related but different things.
Different data providers can classify borderline chances differently.
What the label is trying to capture
Traditional shot totals give every attempt equal weight. A big-chance tag separates a subset of situations that the provider judges to be especially favourable for scoring, making a box score easier to interpret than shot count alone.
Opta's published definition focuses on situations where a player should reasonably be expected to score, including common one-on-one and close-range scenarios, and automatically includes penalties.
Big chance is not the same as xG
A big chance is a category: the event either receives the tag or it does not under the provider's criteria. xG is a continuous probability estimate, allowing two high-quality chances to receive different numerical values.
The concepts can overlap because big-chance status may itself be one of the variables in a provider's xG model, but the metrics should not be used as interchangeable labels.
Big chances missed
A provider may record that a player missed a big chance when the favourable opportunity did not become a goal. That can add useful context to a match in which a team created excellent situations but failed to convert them.
Like all event data, the number should be read with the underlying chances. Two missed big chances can involve very different shot locations, pressure and goalkeeper actions.
Why websites can disagree
Because this is not an official competition judgement made by the referee, another provider can use different thresholds or terminology. A fan comparing apps may therefore see a different big-chance count for the same match.
Consistency matters more than pretending the label is universal. Use the same provider when comparing teams and treat the definition as part of the statistic.
Source check
Sources and further reading
KickVerse uses primary governing-body material where a rule or competition format has an official source. Analysis terms can vary between data providers, so provider-specific definitions are identified rather than presented as universal laws.
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