I still think that Kozak needs a chance as Gestede doesnt really help Sinclair, as his feet dont do much, other than make him jump up.
Kozak can at least play a bit other than head the ball, and would be better with Sinclair to feed off / hold ball up.
Given Sherwood's "tactics" atm, surprised that he hasnt tried Kozak ( at least up front but you never can tell )