His first way back into reckoning was when Lodi got injured as a left back/wing back in tandem with Carrasco.
Saul then had some injuries then lost form and Simeone's relation with him deteriorated.
Hector Herrera should have been his replacement but he either is always injured or not that convincing.
So, Simeone tried Lemar as a left sided box to box and so far things have worked like a treat.