Simples, Bruce is picking a team to counteract a big physical Charlton team, Koren hasn`t done anything in the last few games and will benefit from a break, plus Bruce will be the additional `muscle` required to see these off.. Same tactics used at Millwall to counteract their physicality
I think SB has registered that for all their ability City can be bullied by aggressive teams. The Sheff Wednesday game demonstrated that and to the manager's credit he's making the changes he sees as necessary against the merits of each opposition team. It's bound to be unpopular with some fans, but Bruce backs his own judgement and so far he's been right most of the time.
I bet some of those spitting feathers after 'not signing striker on deadline day' feel proper Charlie's now.