Matip has been missing from action in Liverpool's last three encounters after suffering an adductor injury during the Reds' 1-1 draw against West Brom on 27 December.
Klopp had previously stated that Matip is "in a good way" as they "try" to get him fit for this weekend's clash against Manchester United at Anfield.
However, the 29-year-old has so far failed to return to full first-team training this week. Instead, he has been training alone with Liverpool's physios in a specially-tailored programme at Kirkby.
Whilst Matip's involvement remains unlikely, Klopp insisted he is "close" to returning but a final decision will not be made until closer to the game.
"Joel is close. Does it now make sense to throw him into a game with one or two sessions, which he didn’t do yet, but today and tomorrow he might be involved?" Klopp said.
“To bring him [in], I don't know. We have to see, we have to decide, we have to look at him and how he will train, how he looks in training and these kind of things, but we have still different solutions.
“Hendo is very important in midfield for us as well, so we just have to see. It's not decided yet, why should I?"
Meanwhile, Keita has been sidelined with an ankle injury since impressing in Liverpool's 7-0 victory over Crystal Palace on 19 December.
Like Matip, the Guinean hasn't been present during training at the AXA Training Centre this week and Klopp admits the clash against Ole Gunnar Solskjaer's side comes too soon for him.
“Naby is not ready for involvement. It’s not a big thing; it’s a little bit like with other players in the past when they came back from injuries and then because of the amount of games and situation in the squad they had to play," the boss said.
“Then a little injury happened again. Now we just had to put on the brake and say ‘let’s settle it properly’.
“In the moment we have alternatives in midfield, so we really try to give him all the time he needs to get 100 per cent fit. That’s the situation, so no, he is not in contention for Sunday."
Both Matip and Keita will undoubtedly be required over the coming weeks as Liverpool enter one of their busiest periods of the season, so erring on the side of caution makes sense for the Reds boss.