Kepa Arrizabalaga was restored to Chelsea's starting line-up for Saturday's Premier League clash against Southampton, with Edouard Mendy injured.
And while the Spain gloveman made a couple of good saves, he made an error for Che Adams' equaliser, with the game ending 3-3.
Mendy was back between the sticks for Tuesday's Champions League visit of Sevilla, and the summer signing from Rennes kept a clean sheet as the Blues drew 0-0.
The Senegal keeper has been installed as Chelsea's No1 after a series of high-profile errors last season from Kepa.
But former England striker Darren Bent fears that Kepa's mistakes could land Lampard the sack if Mendy is sidelined again.
Bent said he would play Chelsea's technical adviser Peter Cech over Kepa, after the 38-year-old was this week surprisingly named in the club's Premier League squad.
“I would pick anybody except Kepa,” said Bent, speaking to talkSPORT. “I probably would go Petr Cech over Kepa but then you think to yourself that he has no confidence already, it is gone, it is on the floor, he has got none.
“If you go and play Petr Cech over him as well, what happens then? But what else can you do?”
Bent added: “Every time he plays Kepa he makes a mistake, he costs us goals and he costs us points.
“If you keep putting a goalkeeper out there and he keeps making mistakes, costing you points by the way, you can't keep putting him out there.
“He might cost Frank Lampard his job if he doesn't win many games.”
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Bent's warning comes after reports Chelsea owner Roman Abramovich is lining up Max Allegri as a potential replacement for Lampard.
This article was most recently revised and updated 3 years ago