Kepa was dropped from the starting line-up in Chelsea's last two matches after his error cost the Blues in their 2-0 Premier League defeat by Liverpool last week, with Willy Caballero starting in goal since.
Chelsea also signed goalkeeper Edouard Mendy from Rennes last week to provide competition, but Lampard said it did not mean Kepa would be leaving now or in the January transfer window.
"I certainly won't go to the point of saying Kepa has played his last game for Chelsea," Lampard said. "We have to also understand Kepa is a young man. A lot of the spotlight on him has become unfair.
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I have to protect him because I know he's a good lad trying to do his best.
Mendy was unavailable for the weekend's 3-3 draw at West Brom but Lampard said the 28-year-old would be in the squad for Chelsea's Carabao Cup clash with Tottenham on Tuesday, along with new left-back signing Ben Chilwell.
However, Lampard confirmed wingers Hakim Ziyech and Christian Pulisic were "still in their recovery stage" and would not play a part.
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Chelsea play a Spurs side who received a bye into the last-16 after third round opponents Leyton Orient had players test positive for COVID-19, leading to the match being called off.
Spurs have a congested fixture schedule, with a Europa League qualifier against Maccabi Haifa on Thursday, but Lampard said he still expected manager Jose Mourinho to name a strong line-up.
"I know for Jose it's a busy time with the Europa League," he said. "When I analyse Tottenham and see the squad that didn't play 90 minutes yesterday, I see a very strong squad."
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