The 24-year-old missed nine games through injury, with Liverpool missing his creativity from the left flank.
“We have a specific solution and then we will think about the next game. We will try to figure out which one works best,” he told reporters, with Mane away on duty at the Africa Cup of Nations with Senegal.
“There is no player exactly like Sadio. But it is not a problem, we will find solutions.
“We know there is a difference between fit and match fit, but of course it’s Phil, we have another three days to prepare him for United.
“It was the best news [of the night] at Southampton, that Phil is back. You can see immediately how important it is.
“He will of course not be 100 percent, but he can be important for us, and it is good he is back.”
Henderson is believed to be the most likely to take part against United, having spent less time on the sidelines, but both are arguably as important as Coutinho.
The reintroduction of Coutinho could see Klopp change his personnel in attack, with Firmino likely to keep his place but only one of Origi or Sturridge set to line up with them.
Adam Lallana started in a more advanced against his former club at St. Mary’s, but has proved more effective in the middle of the park this season, and should drop back into that role.
Can, who turned 23 on Thursday, has struggled for consistency this season, but has been tasked with a variety of duties.
When serving as a roving No. 8, he has been largely impressive, but with Klopp’s options improving, there is no guarantee of a starting place for many of his first-team hopefuls.