Kepa, 25, is facing a fight to save his career in west London after being dropped from the starting lineup in favour of 39-year-old Willy Caballero. There's also fresh competition for places following Edouard Mendy's arrival from Rennes for a fee in the region of £20 million.
Mendy could make his debut in Tuesday night's Carabao Cup fourth round clash at Tottenham Hotspur as Kepa is linked with a loan move away from the club, having joined Chelsea as the world's most expensive goalkeeper in 2018 after arriving from Athletic Bilbao for £71.4m.
Kepa has been ridiculed for a series of high-profile mistakes -- including in the Blues' win at Brighton on the Premier League opening weekend -- but Lampard said: "I certainly won't go to the point of [saying] he's played his last game for Chelsea.
"I think it has been a difficult time for Kepa. That's been well documented. I know it, he knows it, but we certainly shouldn't jump to that conclusion.
"Also, [something] which I felt quite strongly about in the last week, is to understand that Kepa is a young man and an awful lot of the highlight or spotlight on him has become slightly unfair.
"I have to protect him because I know he is a good lad and playing with absolute professionalism and intent to do the best he can, as all the squad have done. That's all I want to say about him now."
Chelsea are expected to make a raft of changes from the team which drew 3-3 at West Brom on Saturday. Ben Chilwell is in line to start after making his debut in last week's third round win over Barnsley but Hakim Ziyech (knee) and Christian Pulisic (hamstring) are still unavailable.