The clue Heller is speaking is the case himself. The basebal guy is physical similar to Patrick Jane and his wife is equal to Patrick´s wife Angela, you can see that by the painting. Therefore Patrick quickly knew the answer because his wife did the same to him, causing him to "transform" to his alter-ego Red John and stopping her moving out, the worst way possible. Red John is in fact the male and violent prone version of Jane. His aversion to guns and being a coward regarding confrontation, created probably by some past trauma, a new persona that is everything the oposite of Jane, just keeping is twisted sense of humor and inteligence.