Perhaps due to the trainers inexperience or - simply due to a fight perhaps not going to plan and there needing to be a Plan B which the assistant trainer in the corner may bring with his insight.
There are many good trainers - absolute fantastic at all of the technical stuff - however they may not be good talkers and as such someone else in the corner who can talk sense is a good thing.
Another trail of thought is - perhaps the trainer has said to Powell - "I am not getting through to him - have a word will you??"
In response to Spuds quote above
Am sorry but it just seems like he does it in a lot of fights or I would'nt have bothered to post this topic!!!
And I don't think a trainer would normally ask him to speak. Normally a trainer would have another guy assisting him who would give some input!
If your employed to do cuts then do cuts!!! Paddy Byrne is heralded as one of the best and I know for a fact he does not interupt the trainer! He is good at his job because he does what is required of him and he has been all over the world because of it! Mikkel Kessler etc