When I think about it more I think Lucho, found his emergency CB solution in Digne.
When the stars align in the worst possible way with Pique-Masche being out and Umtiti and Mathieu only being available and one of the two either getting injured in game or feeling a knock or just getting subbed of for rest this is where Digne comes in.
assuming Lucho also doesn't call up Marlon etc either. I'm not talking about using him every now and then there but in the very rare case like what happened today. He also played as a CB for the final 20 mins vs Hercules during the first leg during the Copa Del rey.
I trust Digne to play as a CB than Roberto and it prevents us from having to handicap Busi.