Could be that RB's style of play is exposing Keane's weaknesses.
I definitely remember Keane putting in some MOTM performaces last season - when he stood in the box and headed away cross after cross in the last ten minutes. But that was when Carlo had us playing conservatively.
To my surprise, RB has us playing more expansively. Especially, he's telling Doucoure to get forward more, he's talked about that a lot. Which is fantastic in one respect because Doucoure has put a lot of juice in the attack. But it's leaving space in front of the back four, and Keane has to handle the ball with the guys in front of him further away. It's so easy for an attacker to get him to cough up the ball, and he's too slow to cover for a mistake.
If we were parking the bus still, maybe Keane would still be having a 'good' season.