Timescales? Not really. The witness statements you see which are prepared for trial are seldom what a lawyer would call a contemporaneous record, taken within minutes! They are often a week or more after the event. Witnesses leave the scene and are found and contacted sometimes weeks later and so it depends what time it takes to see each one and get a statement.
The defence is that the person was never assaulted in the way claimed or at all. On the face of it , the only evidence of injury is the complainant saying there was, which doesn't do any harm to the defence at all. All that proves is that the person is saying it. You have to attack the allegation of kneeing, pointing out such inconsistencies as you can when you are defending, no matter how they could be explained by human fallibility or anything else. You play up how perfectly the witness was watching and his certainty in his version, and then rubbish it, because it differs from the other versions, and the other way about with the next witness. Witnesses get supremely confident about what they saw, and you encourage them in that so the contrast between versions sounds much more damaging than it ought really to be, when you point it out.