Benatia was world class (or thereabouts) one season for Roma; he was a seriously good player for a few seasons in Serie A, but he's been having four difficult years since then. Bad injuries and loss of form and opportunity has seen him decline a lot at Bayern and Juventus.
The question is how much he'll cost and whether it's a loan or a full transfer. Stranger things have happened I suppose, but it's a big ask to assume a 31 year old reserve without any previous Premier League experience is going to come here and perform well, especially in the short term... which makes me wonder why exactly we'd be after him. Bloke's 32 in April. Fallback option if Kos leaves for Monaco perhaps?