The Spaniard should have done better with Isaac Hayden’s header which earned Newcastle a late win over the Blues.
Lampard admitted that Kepa had taken accountability for his errors, but urged the 25-year-old to work on his shortcomings.
“Well he will have to deal with outside criticism; that is what football is,” said Lampard.
“Every player, no matter great you are in your career, the best, the absolute best of all time will get criticised and you have to deal with it.
“I think with Kepa he knows, he’ll be honest that there have been some mistakes that have cost us goals.
“It is the nature of it, so that needs to improve. Goalkeepers may have slightly more spotlight on them, but it is a similar thing, really. I think the important thing for that is not to get too embroiled in what is said on the outside and look at your own game.
“It is always the basics, how hard can I work. That’s not just for Kepa, but for any player.
“If you feel in a lack of form, fight to get it back. Go back to basics.”
Chelsea have been linked with a move for Burnley’s Nick Pope in the January window, but Lampard insisted he is not seeking to add another body between the sticks this month.
Asked if he wanted to recruit another goalkeeper, Lampard added: “I am not looking at it now. I am not affected by criticism from the outside as much. I am aware of it, not affected by it.”
Lampard also said he is not interested in a move for Lille’s France Under-21 midfielder Boubakary Soumare.
“I’m aware of him as a player, but he is not on our radar for this window,” said Lampard. “We played against him, but he is not one on the immediate radar. He is a good player, but he is another club’s player.”