Keita was forced out of the starting lineup after he picked up the issue warming up at Anfield, with James Milner taking his place in the side and Neco Williams on the bench.
Having found a strong run of form of late, it is a bitter setback for Keita, and Klopp described it as “not too cool” as he confirmed he would not be considered for the third-round tie.
“I don’t know exactly what he has, it was the groin, but I can say already that he will not be involved against Everton,” he told This Is Anfield in his post-match press conference.
“That makes it 12 adult players that we have, plus the kids. That’s not cool, we cannot change it any more.
“No clue how it happened, I think it was the last shot in warming up when he felt something. He came in and was limping.
“Everybody who has played football has had this kind of injury, and that’s not nice, it’s painful.
“I don’t know exactly what it is, or how long it will take, but I can say already he will not be ready for Sunday.”
Klopp is expected to make a host of changes for the FA Cup this weekend, with the priority being the Premier League, but while he conceded he would call upon “fresh legs,” he gave no indication of the extent of his rotation.
“What I will not do is tell Carlo Ancelotti the lineup tonight,” he said.
“But I will do what I think is right. Some things I can decide by myself—I will—and some things the medical department will tell me.
“So that means I don’t know in this moment what the lineup will be, but it will be the best possible for us in this moment.
“For this game, as you can imagine, I’m pretty sure that Carlo will not make a lot of changes—having the opportunity to win at Anfield, which didn’t happen for a few years, that’s another big chance.
“But we will have fresh legs, and what we need is support, because the only advantage—they played yesterday, we played today—is Anfield.
“We need support from the first second, and we will see how it will be.
“But it was a tough game tonight, and we have to make sure that we make the right decisions.”