Liverpool are expected to be without six players for the trip to Bramall Lane on Wednesday night, though Alisson and Jota are edging closer to a return.
Speaking to reporters on Tuesday, Klopp revealed that Jota had resumed running outdoors as he recovers from a hamstring injury.
“He was running yesterday outside, on his birthday,” the manager said.
“Everything goes in the right direction, but nobody told me he would be back in team training today. There’s still some time.”
On Alisson, he added: “Obviously Ali is closer, but not available for tomorrow, definitely.”
The goalkeeper could return for the clash with Man United on December 17, with there increasing hopes now that Jota could join him.
Asked about Matip’s situation, however, Klopp explained that the centre-back was yet to undergo a scan, suggesting the swelling around his knee had still not gone down.
That would indicate a bad injury for the 32-year-old, though the timeframe around his layoff is as yet unknown.
“I don’t know it exactly, but it doesn’t look good, that’s something we can say,” Klopp said.
“The scan is not done yet, so we don’t know exactly. It’s not great.
“From the first second it was clear, I spoke to him and he said ‘no’, that’s not good. But how long, I don’t know.”
Matip is likely to be replaced by Ibrahima Konate as the Reds travel to Sheffield, which may have been the case either way as Klopp employs rotation through a busy period.
But losing his No. 32 is undoubtedly a blow regardless, with Klopp taking things one game at a time.
“We lost Joel, so that’s so tough. It’s so tough what’s coming up now,” he continued.
“There’s [no way] to think ahead of the next game, there’s no chance. Focus on Sheffield United, go for it, play the best possible game and keep going.”