I still do not understand it. It is not that he gives us any kind of superior protection defensively in that position where he has to make backward runs. His industry is greatly appreciated and he took nice positions, spread the side but he is not exactly useful in any attacking capacity other than his decent early crosses which have no one to head them in.
The reasoning behind it for TT might have been that he wanted 3 tall centrebacks to control the air vs Westhams giants and still have the captain on the field. I would have prefered Azpi had been rested tho.