Watched him against Bayern in the first leg & he played well enough - hard to judge much more than that as Bayern dominated the possession so heavily. Looks like he has the physicality & technique to become a very good player, but still a big gamble for someone of that age, still could go either way.
If we had our centre midfield sorted, then I'd say it's a good looking signing, but if we bought him would he really be a starter, or improve the team? For me we're pretty heavily in need of 2 CM's that are currently playing at the level we require (e.g. Gundogan + Pogba), even if Sanches becomes a bit of a beast by 21-22 like Pogba has managed that's still 3 years away so doesn't solve our current issues.