It may not happen much in sport, but it's pretty much the basis of all negligence law - reasonable foreseeability, and all that. If you have prior knowledge that someone is prone to injury, and you put them in a situation / give them a task to do where they're more likely to get injured (or, in this case, fail to act if you've just witnessed them getting injured, and then leave them to carry on doing the same task for nearly another hour), then you're on pretty shaky ground. Up until now I would imagine most sports clubs have refrained from making claims because of the floodgates argument, but I wouldn't mind betting that this is something that we'll start to see more and more of now players' wages are getting more expensive and harder for clubs to simply write-off?