Can you imagine a Judo club with only one athlete? One, regardless of the level... Only one, single athlete. Besides that – there's everything. Two dummies, mats, mattresses, gums, springs, dumbbells, weights, there's even a physiotherapist's practice. There are two trainers, one is very old and the other very young. And only one judoka. ()
Even if they destroy 20 dummies, even if they tear all mats to pieces, even if they go through every single technique “on paper”... They have no chances against a competitor who has many of those on a similar or higher level around them. This is, of course, an abstract example, to highlight the situation. But it does happen with combat sports that in some categories in some clubs there are no sparing partners. Somethimes my trainer friends tell me about it. They have to look around, “borrow” some athletes, but it doesn't always work out in the end.
In combat sports you can't prepare on your own, without an opponent.