Regression is his middle name and plays with the most beta energy ever seen on the court. He lacks confidence and can't get out of his own head. Time to send him somewhere and get a contributor in return.
I'm a believer in Keegan's ability to perform both offensively and defensively. His rookie year was more the free and easy Keegan that was an extension of his college stint under the Iowa coaching, with his dad's input, that he received there. Then the intensity of the pro coaching teaching techniques and expectations took a toll on him, wore him down, and eventually stifled him. He turned to defense to display his skills in a more non-confrontational way that is more likely to generate complements rather than criticism.
Keegen's stoic ways are a cloaking mechanism for what is a very emotional and sensitive individual. His dad, Kenyon, revealed that Keegan has a volatile temper and Kenyon worked hard to try to find a way for him to cope with the complexities and frustrations of basketball without outward temper tantrums...and thus we have the present Keegan.
Something in the manner that he has been coached on the Kings has led to his regression and retraction into his shield. Notice that Kenyon was actively involved in communications during Keegan's rookie year while now he is eerily silent. He knows something is not right but won't actively engage. (Unlike the Bagley clan.)
It is very likely that a change in scenery, or a change in coaching techniques, may draw Keegan out of the doldrums and allow him to develop into a complete player and All-Star that many of us see (or saw) in his future. Hopefully, the development is on a Kings team. But if not, I wish him well wherever he plays.