Johnson is an enigma. Why he's not getting on the court is perplexing. Got to assume Barnes knows what he's doing... whether it's for motivation, to encourage him to leave, JJs on double secret probation, or he just doesn't trust or expect him to contribute.
It is the 3rd game in 3 days. Barnes might be making a change as soon as he see's their intensity off slightly. He's been doing this for 30 years so he'd have a good reason for moving the parts around.