Krafth isn't a full back . Watch him, his instincts are that of a rubbish right midfield player . That space right back to right centre half is a gold mine for opposition. Leeds exploited it in both games with Jack Harrison (when Bruce wisely played a right winger in Murphy there) . This has been a problem all season regardless of personnel. Hayden often sees it and takes it upon himself to plug the gap and that's why you frequently see the hole in midfield as Shelvey either can't be mobile enough or can't be arsed to be mobile enough.
When you try and press as we have since Jones has come in , sides can play over the press or through it . Too many gaps the day for reasons mentioned above and Chelsea have enough good players even without the gaps to get through.