Guys like Chygrinski etc. were huge talents when we signed them.
Were they? Not Chygro, he wasn't the best defender neither at Shaktar nor in the Ukranian NT. I remember watching a couple Shaktar games back when we were about to sing him and thinking...
"Is Pep sure he didn't mean the Srna guy instead?"- Sure, some defenders are slow, and some are unsteady when having to do a pass instead of just clearing it... but not all defenders are the same. There are plenty of CB's faster than Chygro and more comfortable with the ball than Caceres aside from Thiago Silva or Hummels. There's about one or two on every team in the world.
We just tend to sign square pegs and then be surprised when they happen to be unable to fit into round holes. Let me get back to Agger, the guy's good with the ball and not the Flash but fast enough to do the job... but for some unexplainable reason, should we go to Anfield to sign a defender, we would end up with Skrtl, who is completely wrong for us. And then you would come and say
"but of course we can only sign midfielders! Look at how Skrtl, a highly rated CB failed with us!"
How about we sign a CB, but this time we get somebody with half a brain to watch a couple of matches with the intended target and then decide if he will fit, instead of whatever arcane, nonsensical system they've been using up until now?