I don’t think Keane and Holgate would work as a partnership as both are suspect in the air.
It makes sense to complement Holgate’s pace with a big nasty grock who will take no prisoners.
Keane has the movement of a deep sea diver and the positional awareness of a six year old.
Whoever ended up playing alongside Keane, would end up spending most of the game trying to cover for him, which in turn leaves holes all over the place - think of Martina at left back last season and then move those holes into the middle of the defence !
Keane shouldn`t be anywhere near the first team.
Quite simply it has got to be, two new centre halves ( can`t see it being Mina now ) and Holgate.