The Reds host ex-defender Mauricio Pochettino's Saints looking to continue a win of three wins in all competitions and will have several players back from injury at Anfield.
Mané returned to training on Thursday after overcoming a slight hamstring injury that had forced him to return from international duty early, having recently missed five games of the campaign with a similar issue.
The former Southampton winger only made his return at West Ham United in Liverpool's last outing but supplied two assists and lasted 76 minutes despite only resuming full training two days earlier.
He will be monitored to determine whether he can be involved, while Lallana is likely to start on the bench against his former club.
Captain Henderson has also been passed fit to feature after overcoming a thigh complaint which prevented him from facing the Hammers or joining up with the England national team.
Klopp rules out full 90 minutes for Lallana
Klopp told his pre-match press conference that Liverpool "have to wait" on Mané and will make a late decision on him, adding that Lallana "is in training now since three or four days ago."
He explained: "It was a really long [time that Lallana was out]. It is fantastic that he is back. He lost nothing, no skills or anything. He trained really well but in the next few weeks we have games every three days and we will need him for that."
The German insisted that there is "no rush" to bring the England international back in despite the fact that "everyone who knows Adam can imagine how ready he is to be part of the squad again."
"We will see what we do in this case," hinted Klopp, also stating that Henderson "should be okay" because he "used the week he had in the national break" to "recover from different things" and allow him to get "on a good way."
Lallana was one of the Reds' stand-out performers last season and enjoyed his most productive year yet at Anfield with eight goals and seven assists in 27 Premier League appearances.
But despite the fillip of Lallana's imminent return to the pitch, Klopp is eager to remain cautious so as to avoid overloading the 29-year-old.
"It's long ago," he said of the player's injury. "He's a fantastic player but we want to have him for the season. This is the moment where the player wants to be back immediately and I am the bad guy who says, 'not today, maybe tomorrow'."
Klopp insisted his approach is "completely normal" and that he will adopt it for Lallana's long-term benefit, insisting they "will see" when he is ready to make his first competitive start for the club since May.
He warned: "It depends how the other players are, what shape, how fit they are. We will use him [against Southampton] for sure but bringing him now for 90 minutes is absolutely not a good idea and will not happen."
"Surgeons recommended Clyne's surgery"
Liverpool's only absentee of note will be right-back Nathaniel Clyne, who remains unavailable until February. He was forced to undergo minor back surgery having, like Lallana, yet to appear for the club this season.
Klopp acknowledged that "things like this happen" and admitted: "All the specialists agreed, we should try it the conservative way without the surgery. Now everybody agreed we now had to use it [and have Clyne undergo the surgery]."
The Reds boss said that the defender "will be fine" but noted that "it will have been a long time for him" when he finally returns from injury.
Klopp revealed that Clyne is "already in the last period of the recovery" and that despite having gone under the knife, the England international "will be back round about" that level of sharpness.
Philippe Coutinho is fit having missed the Reds' last three matches with an adductor injury.
The playmaker lasted 68 minutes for Brazil against England on Tuesday night and is likely to start against Southampton. Klopp could start with Mané, Coutinho, Mohamed Salah and Roberto Firmino for the first time in a league game.