The Croatia international started at centre-half alongside Fabinho for the cup clash but the World Cup finalist lasted three minutes before being replaced.
Lovren was forced off with a suspected hamstring injury and Liverpool FC’s youngest-ever FA Cup debutant Ki-Jana Hoever replaced the centre-half.
Klopp confirmed that Lovren sustained a hamstring problem in the FA Cup clash.
“[It is his] hamstring, is what I heard – without any signs before. I asked everybody, no signs, nothing, just out of the blue, so that’s the decision you have to make,” Klopp is quoted as saying by Liverpool FC’s website.
“I am not sure what you all would have said if immediately from the beginning our centre-half situation was Fabinho and Ki-Jana; then probably a few very smart people would tell me that I don’t respect the competition or whatever.
“So, we tried to do all the things [we could]. Of course, on the other hand it doesn’t make sense to bring in a 16-year-old boy from the start. You don’t bring him, you wait until he is completely ready, but he did well. He came on and did well. That’s how it sometimes starts – when you are really needed then it is only about if you are good enough and not how old you are.
“He did well, so that was all OK. That’s it.”
Asked about how long Lovren will be on the sidelines, Klopp replied:
“I don’t know in this moment.”
Liverpool FC can ill-afford to lose Lovren to a long-term injury given that Joe Gomez and Joel Matip are already sidelined with fitness concerns.
Gomez could return to first-team action next month after the England international sustained an ankle problem during Liverpool FC’s 3-1 win at Burnley in November.
Former Schalke 04 defender Matip suffered a fractured collarbone during Liverpool FC’s 1-0 win against Napoli in their final Champions League group-stage fixture.
The African defender underwent surgery on the problem and is close to a return to first-team training ahead of their next Premier League fixture against Brighton on Saturday.
Asked about the fitness of both Gomez and Matip ahead of the FA Cup clash last week, Klopp said:
“[Joe is] getting better, it’s getting better, but he is not yet involved.
“Joel is maybe a bit closer, I’m not sure, but hopefully he moves completely normal. We have to see how the bone healing is, that’s always how it is when something [has] broke, but from his movements it looks nearly normal.
“But there are still a few days to go until we can have them in team training, until [Joel] is ready for contact, which for a centre-half is pretty important. Until then we will make all the fitness work.
“The good thing is Joel can do all the fitness work already since a week or so ago, so that means when he will be back he will be 100 per cent fit. Then he has to get rhythm and everything will be fine.”
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