I used to run an outdoor 5-a-side team, rotating subs from a squad of 7.
The ideal number is 6, but I usually ended up with 5 or 7. It was a real pain - a couple of weeks I had 8 players and had to diplomatically sit myself out.
The problem extends to Sunday football too. Two weeks ago we were 2nd in the league, then we comfortably won a cup match 3-0.
A week later we had to travel 25 miles away to face the same team in the league and lost 7-0 in drizzle and wind off the North Sea. Of course only having 10 men didn't do us any favours.
4 players didn't turn up on the day - the goalkeeper later claimed he had fallen down some stairs.