First goal, a really good one, but Skrtel's first movement when Ronaldo touches the ball off to James is far too slow, Ronaldo has taken three steps into the space between him and Lovren before Skrtel tracks him. Skrtel is inches away from getting a foot on the ball, so to my mind if he had tracked Ronaldo even one step out of the three sooner, he makes the clearance. Ball watching will do that.
Second goal. Johnson is marking Benzema in the initial set play, the ball doesn't get cleared and he drifts inside the posts leaving his man to drop into the space behind him. The chip from Kroos is inch perfect and Johnson cannot backtrack fast enough to get a challenge on Benzema who now has all the time in the world to place his header. Johnson leaves his man. Why? Ball watching.
Third goal Johnson marking Benzema on the corner. The ball goes beyond the two of them and Johnson leaves Benzema in favour of taking up a position on the line. Benzema is free and slots home the returned header. Why did Johnson leave Benzema? Ball watching.
Its really basic, basic stuff, but it is the kind of innate response that some "defenders" have in situations when they are watching the play. The very best defenders stay with their man because they know that it only goes wrong when a man is left on his own. Track the man not the ball, mark the man not the space. Johnson and Skrtel will never be good defenders in those situations against quality players, because they are ball watching and miss the movement of the attackers.
Nothing Brendan can do about that except sign players who don't do it.