KT has played on the left of a back 3, so have no idea why he couldn't cover Gabby. We basically play a back 3 anyway, with Zinny next to Partey in a W-M.
Given the Pole can also play LB and DM, I think he could be the long term cover for Zinny. MA's keeps talking about his versatility. Having a young intl who only takes one squad place to cover LCH and LB makes sense. Given the versatility of Tommy and White, that's 6 players covering all the back 4, if KT were to leave to be a regular starter at a top club.
MA doesn't want a winger like KT at LB. He wants a ticked in MF.