His trainer Richard Olsen is doing a good job with Kessler, his been training him since he started boxing, so they know each other extremely well! For his last couple fights they have been working with an american trainer Montoya (cant remember firstname) and he says Kessler dont need to change his style, but he should go more for the body when he fights! he also stated Kessler probably could have beat Joe if he had throw some heavy bodyshots, intead going for the head all the time!
He doesn't only need a new trainer. He needs additional trainers. Richard Olsen have some virtues but tactics/strategy is not one of them. Montoya-Olsen and perhaps some guy that can improve on Kessler's foodwork a bit would do it for me.
He needs someone to be able to take him more into the main stream before its too late,promotionally that is
Kessler can not fight on the back foot and has limited counter punching skills so I think he needs a trainer that can show him something new.