The Athletic's James Pearce relayed the news on Twitter:
Fabinho has been absent since November with an ankle injury, while a knee problem has limited Matip to just one appearance since September.
The manager also offered an update on the other players in the Reds' treatment room:
Dejan Lovren has been out for over a month with a muscle injury, while James Milner hasn't played since he limped out of Liverpool's 1-0 FA Cup win over Everton after nine minutes on January 5.
Naby Keita suffered a groin injury in the warm-up ahead of Liverpool's 2-0 win over Sheffield United three days prior.
Liverpool host United at Anfield as they look to continue their Premier League title charge.
The Red Devils are the only opponents Liverpool haven't beaten in 21 league games this season, and Klopp wants to see his side perform against their bitter rivals.
He said: "It's a very, very important football game. Very important. We have to learn how to deal with games like this in the right manner. We haven't done bad in the past, but we can still improve."
He is expecting a defence-first approach from United:
Aside from their first meeting with United, which ended in a 1-1 draw, Liverpool have steamrollered all before them this season.
Only Manchester City have scored more than their 50 goals, and no team comes close to their defensive record of just 14 conceded.
Given United are no longer the team they used to be under Sir Alex Ferguson, their reluctance to go toe-to-toe with the Reds is understandable.
The two sides have drawn more often than not in recent meetings, with six stalemates in their last eight matches against each other. That should give United hope of avoiding defeat once again, but Liverpool did run out 3-1 winners the last time they visited Anfield in December 2018.