It's 5:47pm on Tuesday. Three messages land in the WhatsApp group: "Sorry, can't make it tonight." You had 10 confirmed. Now you have 7. The round-robin you planned for 8 doesn't work. You have about an hour to figure out a format that gives everyone fair playing time, and you haven't even left work yet.
This is the Tuesday Night Problem. It happens every week, at every club, in every racquet sport. The number you planned for is never the number that shows up.
Why Odd Numbers Break Traditional Formats
A round-robin for 8 players is clean. Four matches running simultaneously, everyone plays 7 games, done in two hours. Remove one player and the maths stops working. With 7 players, someone has to sit out every round. That means bye rotations, which means unequal rest times, which means complaints.
It gets worse with prime numbers. 7, 11, and 13 players are particularly awkward because they resist clean division into groups. You cannot split 7 into equal groups. Two groups of 4 and 3 means one group finishes earlier, and the cross-group matches never happen.
The real issue is that traditional formats assume a fixed number of players. The moment reality deviates from the plan, the format breaks.
Practical Solutions for Common Odd Numbers
Here are concrete approaches that work, tested across hundreds of club nights.
7 players: Run a full round-robin with rotating byes. Each player sits out one round, plays six matches. Post the bye schedule visibly so everyone knows when they are off. The key is ensuring the bye rotates fairly. If the same person always gets the first or last bye, it feels unfair even when it is not.
9 players: Split into three groups of three for a first phase (each player plays 2 matches), then re-seed into three new groups based on results. This gives everyone 4 matches in roughly the same time as a clean 8-player round-robin.
11 players: Two groups of 4 and one group of 3 for a first phase, then cross-group matches for the second phase based on standings. Alternatively, run a Swiss-style format: pair players based on current results after each round, with no fixed groups.
13 players: Swiss works best here. Fixed groups become unwieldy. Four rounds of Swiss pairing gives everyone 4 matches with progressively better-matched opponents.
Any odd number above 14: Use a drop-in format. Forget fixed groups entirely. Generate pairings round by round for whoever is present and available.
How Drop-In Format Solves This Permanently
The cleanest solution to the odd-number problem is to stop planning for a specific number altogether.
In a drop-in format, there are no pre-set groups. Each round, the system looks at who is present and available, considers their current rating, and generates the best possible set of pairings. If one player has to sit out, the system rotates byes automatically. If someone arrives late, they are included in the next round. If someone leaves early, the remaining players are re-paired without disruption.
This works because the format is not built around a fixed bracket. It is built around the players who are actually in the room right now.
Tools like ServeLeague handle this automatically, generating balanced pairings based on current ratings for whatever number of players are present. But even without software, you can run a manual version: write all present players on cards, shuffle, pair them up, and rotate the odd one out.
Handling Late Arrivals and Early Leavers
Odd numbers are not the only variable. Players arrive late, leave early, or need extended breaks between games. A rigid format treats all of these as problems. A flexible format treats them as normal.
Late arrivals: Slot them into the next available round. Do not restart the schedule. In a drop-in or Swiss format, they simply join the pool. In a round-robin with byes, they take the next available bye slot and begin playing from the following round.
Early leavers: Their completed matches count. Their remaining matches are recorded as walkovers or simply not scheduled. In a rating-based system, only played matches affect ratings, so leaving early does not distort the standings.
Extended breaks: Some players need more rest between games, especially in physically demanding sports like squash or badminton. A good scheduling system accounts for this by spacing out their matches. If you are scheduling manually, keep a "rest priority" list and give the longest break to whoever played most recently.
Building a Culture Where Cancellations Hurt Less
You cannot eliminate late cancellations. But you can reduce their impact.
Standby lists. Maintain a list of players who want to come but did not make the initial cut. When someone cancels, message the standby list. Even a 30-minute notice is enough for someone who lives nearby.
Waitlists with automatic promotion. If your session has a capacity limit, operate a waitlist. When a spot opens, the first person on the waitlist gets notified automatically. No manual texting required.
Overbook slightly. If your ideal number is 12 and your no-show rate is about 20%, confirm 14 or 15. You will occasionally have a few extra players, but a drop-in format handles that gracefully. It is much better to have 13 than 9.
Normalise cancellation. Clubs that punish cancellations (charging no-show fees, removing people from the group) create anxiety. Clubs that treat cancellation as a normal part of adult life, and design their format to absorb it, build loyalty.
The best club nights are not the ones where exactly the right number of people show up. They are the ones where it does not matter how many people show up. If your format breaks every time the headcount changes by one or two, the format is fragile. Switching to a system that generates pairings round by round, for whoever is present, removes the single biggest source of organiser stress on club night.
Seven players is not a problem. It is a Tuesday.