Keita, a £52.75m signing from Bundesliga club RB Leipzig, came on as a half-time substitute in the International Champions Cup loss at the Bank of America Stadium in Charlotte.
Liverpool were leading at the break thanks to Virgil van Dijk’s header but collapsed in the second period as a Christian Pulisic brace and Jacob Bruun Larsen effort settled the contest.
Keita has featured heavily in pre-season and Klopp admitted the Guinea international was “exhausted”.
When asked about Keita’s performance, Klopp replied: “He can do much better, that’s clear.
“He was exhausted, he was really done in the last few minutes when they scored on the counter-attack. Usually Naby is fit and around the situation. I think it was the third goal, he couldn’t do it anymore.
But, football-wise, he is in a very good way because he’s a naturally skilled player. In small spaces his first few yards are outstandingly quick, so that changed the situation a lot.
“He was good in the game and then the last game, maybe the half-time was 10 minutes too long for him.
“Today it was very intense for both teams; we trained this morning harder than we usually would do on a match day but that’s how pre-season is.
“We still could have won the game but we didn’t. We have to talk about it because you ask questions but we don’t have to think too long about it.”
Keita, who hit nine goals for RB Leipzig last term, took up an advanced midfield role against Borussia Dortmund.
The 23-year-old is expected to be used as a box-to-box midfielder at Liverpool but Klopp is excited by his versatility.
“He is a creative midfield player with discipline; tactical discipline is a big strength of his usually,” the German said.
“He’s doing the right things in the right moment, that’s how good players are.
“I don’t want to give him 500,000 [pieces of] information. We got him because he is the player he is and now we want to work with that. That means first of all we let him go and adapt to our system.
“I see him as an ‘8’, he can play ’10’ as well, maybe in the future he can play ‘6’ as well. At Leipzig, he played as a winger, that’s for sure not his best position but he can play it because he has the speed for it, he has the football intelligence for it.
“We see him as a creative No.8 playing the passes and making the runs with the ball. With the ball he has the same speed as without, you don’t have a lot of players with this quality.
“We know what he’s good in and we try to fit it into our game, but that should not be a big problem.”