The back-up goalkeeper has given Thomas Tuchel a major dilemma ahead of that showdown with Palmeiras on Saturday.
The £71million Spaniard produced two crucial second-half saves as Chelsea’s nerves got the better of them in Abu Dhabi and Saudi Arabian side Al Hilal threatened to cause a shock.
Leading through Romelu Lukaku’s first half strike, the European champions suffered a wobble late on as their opponents grew in confidence and for the second time in as many games, it was Kepa who came to their rescue.
First, he was down sharply to deny Moussa Marega in a one-on-one and then produced a spectacular save when pushing Kanno Mohamed’s long-range effort around the post.
On Saturday, it was his extra-time penalty save that killed Plymouth’s hopes of an FA Cup upset.
The question now is how Tuchel plays it from here.
Earlier this week, first team coach Zsolt Low refused to offer any guarantees Kepa would hold onto his place following Mendy’s return to the fold.
The Senegal international is indisputably Chelsea’s No1, no matter Kepa’s form in his absence. But to drop him straight back into the team on Saturday would be a big call – and undoubtedly harsh on his understudy.
While Kepa holds the status of ‘cup keeper’ this competition presents something of a grey area.
Had Mendy not been on AFCON duty, would he have maintained his place in Abu Dhabi?
The domestic knockouts are one thing but it is Mendy who plays in the Champions League.
It is a delicate and, perhaps, pivotal moment in Kepa’s rehabilitation at Chelsea.
Under Tuchel he has rediscovered his confidence and some of the form that made him the most expensive keeper on the planet when moving from Athletic Bilbao in 2018.
Whether he will ever be able to justify his price tag is questionable but he has become a figure of growing importance since Tuchel’s arrival.
The German has managed to keep him interested and involved, helped, not least, by Chelsea’s success in cup competitions over the last 12 months.
Kepa was the shoot-out hero in the Super Cup at the start of the season and has impressed on their run to the Carabao Cup Final, which gives him another chance of glory at the end of the month.
But beyond that Wembley clash with Liverpool there will be few opportunities for the remainder of the campaign, with his games likely to be limited to the FA Cup.
Should Tuchel drop him on Saturday it risks seriously damaging the relationship between the two.
One of Tuchel’s strengths has been to keep fringe players involved and it feels unlikely he would be prepared to jeopardise the work he has done with Kepa over the past 12 months.
Under him the 27-year-old has gone from misfit to a growing cult figure among fans, given his increasingly key contributions.
This time last year his days at Stamford Bridge looked numbered and the future still remains uncertain for a keeper with greater ambitions than merely to be a No2.
But Saturday represents the chance to win his second piece of major silverware this season and another important step on his road to redemption.
Surely Tuchel cannot deny him that?