I got round to reading this article now. It's very interesting - and covers a subjects that's probably as of yet underdeveloped in football.
The way I see it (and I don't think it's happening much yet), analysts should be working with match data in real-time to look at things like available areas of play and other things that help figure out what spaces are available or need to be plugged on the field. They can then communicate their observations to an assistant coach who can make recommendations to the main coach. Are there any rules against players have some kind of earpiece? (I suppose most are annoying physically, but probably something could be developed that players could wear that's not dangerous and does not interfere with their play.) Cause once you have that in place as well, then the tactical battle can really go up a notch, with coaches directing team shape and actions in real-time to react to what the opposition is and isn't doing - kinda like what's happening in American Football already, except without all the breaks in play.
Even with all the stats in the world in play and used correctly, not every transfer won't be a success. Football is a complex game, and stats anyway can't take into account how tactics and personnel might change at the player's new club and how that might affect him, or what else might happent to a player's form. (And in Keita's case, it doesn't help either that he is injured all the time.) Also, if Keita is the only high-profile failure among Liverpool's transfers since they went all-in on analytics, then their transfer business has become a lot more effective than it used to be. (Low-key transfer fit a different conversation, since more risk can be taken with those.)