As the recent Australian Open highlighted, players retiring in the middle of a match is quite a common occurrence. This was illustrated when World Number One Rafael Nadal had to retire in the fifth set of his quarter-final against Marin Cilic with a leg injury. Two days later, surprise semi-finalist Chung Hyeon’s challenge for the title came to a premature end when the South Korean was forced to quit his match against Roger Federer due to blisters on his foot.

And then occasionally there are disqualifications, as happened, for example, when Canadian tennis player, Dennis Shapovalov, hit a ball at the chair umpire during a Davis Cup tie against Great Britain.

But what happens to bets which have been placed on a match in the event that a player is forced to withdraw, or, in more extreme circumstances, is disqualified? What are the rules which govern tennis betting?

Essentially there are two different outcomes, depending on the bet, online betting site chosen and bookmaker. The first outcome is that if a match is not completed, then all bets are deemed void. The alternative is that the player progressing to the next round is considered as having won the match, even if their opponent has retired, provided that the first set has been completed. However, if the match has been abandoned before the completion of the first set, then it is normally regarded as void. These rules apply equally to singles, and to doubles, matches.

There are refinements to these basic rules. For example, once a player has started a tournament, any bets on their progress in the tournament – for example, to reach the quarter, semi, or final stage - are deemed valid, even if the player subsequently retires during the early rounds of a championship. Only if they fail to start the tournament at all are bets on them deemed void.

Where bets are placed on the number of games or sets within a match, then a retirement or withdrawal will render bets on that game or set market void. There may be variations on this, depending on the bookmaker.

For example, in a 5-set match, if a retirement occurs before the completion of the fourth set, then normally any bet on the number of sets won by either player will be deemed void. However, if it occurs in the 5^th set, as was the case with Nadal in Melbourne, then the result will be determined as if all five sets had been completed.

All bets where the outcome has already been decided at the time of the retirement or withdrawal are considered valid, and will be settled accordingly. For example, if a bet has been placed on Player A to win the first two sets, and they retire in the third, then those bets stand because the outcome had already been decided. All bets, however, where the outcome has not been decided, are considered void.

With injuries a frequent problem for the top tennis players, retirements from matches are a fact of life and will have an impact on the result of online bets. The rules in such cases are usually clear and consistent but it is better than the bettor knows where they stand in such circumstances.