Anastacia is the person (of those involved) with the least idea of what goes on, on Strictly.
Brendan has 14 Series of experience of what can happen, but that has changed a lot over the 14 Series.
The producer is the one who has control of the most things, and may be making new rules up on a minute to minute basis.
It's also an entertainment show, and not a 'real' competition, so decisions are made for other reasons than fairness.
I am just a punter on Digitalspy who has almost no certain information to go on.
I don't know where the idea has come from that Brendan was also injured on Friday?
Some injuries are easier to assess than others. If this is a deep soft tissue injury, then it could require an MRI scan for a consultant to be able to get the best idea of the extent of the injury.
Doctors working off feedback from Anastacia about the symptoms she feels, would have to make an educated guess.
When you factor in the timescale and that things (such as Brendan and Anastacia trying to come up with a routine that she can do which will not injure her further), then you can see how it can become a whole mess of decisions, all made at short notice, with limited information. Each decision taken can limit options for the future.
One thing they can't then do is go back to the previous day and start again.