I disagree. People like Skrtle, Sakho, Lucas... they are fighters. They give 100% as far as I can. They're just no top quality - that's not their fault.
Lucas's game is limited. We've know it for years. good at reading and breaking up the oppositions' play, but poor control, poor passer, prone to give away free kicks and no goals in him at all.
Can isn't mature enough. Often mis-controls the ball and makes the wrong choice in terms when to pass and when to carry on with the ball.
Sakho... he's just clumsy and looks very uncomfortable on the ball. Bambi on ice.
Fact is, we just haven't invested in quality.