Frank Lampard was left to rue Chelsea's "basic errors" after they failed to see off 10-man Arsenal on Tuesday night.
The Blues twice led against their London rivals after David Luiz was sent off on his return to Stamford Bridge, with Jorginho netting from the penalty spot and captain Cesar Azpilicueta scoring six minutes from time following a Gabriel Martinelli equaliser that came after a slip at the crucial moment from N'Golo Kante.
However, Hector Bellerin struck late to secure a point for Arsenal after cutting inside and being allowed to shoot with his weaker left foot.
Lampard was particularly unhappy with the defending for that second goal and called on Chelsea to work hard in order to eliminate such simple mistakes.
"We created enough in the second half, but didn't finish our chances and made errors which show us where we are at. Basic errors can cost you points," he told BT Sport.
"Their (second), it is a goal you see every day in the park - the right-back rolls it onto his left foot, and that can't happen.
"If we want to get where we want to be, and we are in a process here, then we have to stop that stuff because we can't get anywhere like that.
"It comes with hard work, in training and on the pitch."
