Klopp faces the prospect of having no fit centre-backs for Friday's FA Cup third-round trip to Exeter.
Dejan Lovren limped off during the first half of Tuesday's 1-0 League Cup semi-final first-leg victory at Stoke after pulling a hamstring.
Martin Skrtel has already been ruled out until February with a similar injury, while Mamadou Sakho missed the match at the Britannia Stadium with a knee problem.
Liverpool have edge after Ibe winner at Stoke
Kolo Toure, who came in for Sakho against Stoke, was limping with cramp towards the end, and Klopp is unsure if he will be fit for Friday's game. And teenager Joe Gomez is a long-term casualty with serious knee ligament injury sustained in October.
The Liverpool manager said: "In this moment with no centre-back fit, I would say it is a situation where we have to think about going into the transfer market.
"Two weeks ago we had three centre-backs, that's a good situation. At the start of the season, we had five. Now we have none.
"We now have three injured centre-backs and the only fit one got cramp near the end, so that was not the funniest thing in the world.
'Angry' Klopp urges Liverpool to raise game
"I don't know if any of our central defenders have a chance of being fit. Sakho, I don't think so. Kolo said it's only a cramp. But I don't know for him either."
Liverpool suffered further injury problems at the Britannia Stadium as playmaker Philippe Coutinho limped off with a hamstring problem during the first half.
Klopp now has 11 members of his senior squad unavailable, having seen them suffer 24 separate injuries between them since he took charge at Anfield in October.
The Liverpool manager said that the injury troubles overshadowed what he felt was a much better performance from his players following the disappointing display they produced in losing 2-0 at West Ham in the Premier League last Saturday.
Klopp said: "It is a little bit of a strange feeling because on the one side we have won this game and played well. The fight was great.
"I was really angry last week, but now I'm proud because we have reacted so well in such a difficult game in all parts."
Liverpool will be favourites to secure a place in the final at Wembley when Stoke visit Anfield for the second leg on January 26.
Stoke manager Mark Hughes, though, feels that his team are still very much in with a chance, despite their first-leg defeat.
He said: "Liverpool had the benefit of the goal, and the first goal in semi-finals is key.
"As a consequence of that goal they could drop deeper and protect it.
"We dominated the second half but we didn't get that break. The key was that we didn't concede another and that was a danger. We are still in the tie.
"We have the capability to get back into it. There are pressures when you are the home side so you can use that as the visiting side.
"We are not deflated by the performance or the result but the key is we are still in it."
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ