Players get injured in rugby league it kind of goes with the territory. It's hardly as if Peacock was walking down the street minding his own business when his knee went or he can't get out of bed for two days after a match. That's the time to retire - not now.
When he returns I expect he'll get injured again at some time in the future and I also suspect he'll eventually decide to hang up his boots but as long as in the meantime he is earning selection I'd like to have him around the team. He's having a fantastic season - when not having to play while carrying a knock.
Was the injury he picked up at Huddersfield on the same knee that got buckled at Bradford in the previous week's match? Shows how important he is to the team that the coach didn't appear able to afford the time for that injury to settle/recover before sending him in to battle again - but perhaps that's a symptom of starting the season with a barely adequate squad and unloading a fit and healthy 1st grade International prop from within it that you used in 32 games out of 37 in 2012 while also not showing faith in the remaining alternatives.