Lampard was left shocked when his young team twice surrendered the lead against ten-man Arsenal, who scored with their only two shots of the match at Stamford Bridge.
He said: “When you go 2-1 up with five minutes to go you have to get the basics right. We gifted them their first goal and the second goal was also soft.
“For a right-back to be able to cut inside and roll it into the far corner is too soft. We have to be honest about that.
“It's the same old story of creating a lot of chances and not taking them and we have to take a look at ourselves for that.
“Their first goal came because N'Golo Kante slipped over but that wasn't the error that cost us. It came on the edge of our own area because people ran forwards when they should have been running back."