75% of a midfielder's defensive contribution is being at the right spot and taking up the physical space. This requires constant movement to close off passing options, being there not to allow the opponent space and time to turn, moving in to support a teammate that is liable to be dribbled past.
I'd say 2 out of 3 games we play, unless the opponent is out of balance, there are at least two defenders on whoever has the ball for us. Wingers face two guys when they're dribbling, Messi faces 3 or 4 in the middle.
Meanwhile, when they have the ball, there are almost always only one defender on the opponent with the ball.
It doesn't matter if you're Van Dijk or Riqui Puig, two defenders are always better than one.
This is where we're shit defensively. It's got nothing to with our players being physically weak or bad at tackling. We're bad because we simply are not there. We don't outnumber them like they do to us. This is not something Rakitic fixes in anyway or any other physically strong midfielder for that matter.
It's about disciplin, confidence and young players who can run.