Chelsea manager Frank Lampard said his team were "so awful for 30 minutes" against Arsenal before mounting a late comeback to win 2-1 on Sunday in the Premier League.
Lampard told reporters he had to deliver a firm half-time team talk to rouse his players after they went in at the break trailing 1-0 to Pierre-Emerick Aubameyang's early headed goal.
"We were so awful for 30 minutes, slow lethargic, nervous. The second half was nothing to do with tactics it was all to do with spirit and desire. From my point of view you can accept a missed pass but you can't accept lethargy in a London derby.