The Merseyside giants went into the November international break sitting five points clear at the summit of the Premier League table and also lead the way in the 36-team Champions League rankings after four matchdays.
Liverpool's dominance has not waned even with injuries to Alisson Becker, Diogo Jota, Harvey Elliott and Federico Chiesa, while Trent Alexander-Arnold also suffered a hamstring strain in the 2-0 win over Aston Villa two weekends ago.
Captain Virgil van Dijk was also sent home early from international duty with the Netherlands, but speaking to the media in Friday's pre-game press conference, Slot confirmed that the Dutchman was fit and ready to go for Southampton.
Elliott is also back in training two months on from breaking his foot, but Slot had less positive news to share on Alisson, Alexander-Arnold, Jota and Chiesa, all of whom are set to miss the trip to St Mary's.
Van Dijk back but Alexander-Arnold to miss Southampton
Starting with Alisson's fitness, Slot said: "We are careful with everyone, especially when it comes to muscle injuries. But he is back in training with the goalkeeper coach.
"He is not training with the team yet, but that is expected to be done soon, and then let's wait and see where he is in terms of match fitness. But he is getting better and better, but not ready to play [on] Sunday.
"Virgil is all good. He is training with us today. Trent isn't training with us yet, but he is getting there so we expect him to be back with us soon. Harvey is training with us again so that's the positive thing, he has been out for many weeks but he is on the training ground again with the team. So, that's a positive thing for him.
"Jota is still apart from the group, same as Federico, who is coming back into the session maybe in one exercise today. They are all expected to be back within now and a few weeks, but the last part of the recovery is always the most difficult one. So, let's wait and see. But Virgil is completely OK."
Conor Bradley is expected to fill in for Alexander-Arnold in Sunday's clash with basement side Southampton, while Caoimhin Kelleher will continue in between the sticks while Alisson recovers from his affliction.
Will Alisson, Jota, Alexander-Arnold be fit for Real Madrid?
The trip to Southampton comes just three days before a Champions League reunion with Real Madrid at Anfield, where Alexander-Arnold might be fit to return, but Slot is not confident that Alisson or Jota will be fit.
"That is something we have to wait and see because I just said that the last few days of a recovery are always the ones that are most tricky," Slot replied when asked if any of the three could face Los Blancos.
"Because then they have to go from isolated training sessions towards the group training session - and that step is always the most difficult one. So, for me it is difficult to judge now and to tell you now if it is going to be one, two or three days or a bit longer.
"The only thing I can say is that with Alisson and with Jota, I don't expect them to be available for that game. With Trent, it's going to be in between."
Victory on Sunday would see Slot become just the third manager in Premier League history to win 10 of his first 12 games in charge, but Liverpool's lead at the top of the table could be cut down to two points if Manchester City beat Tottenham Hotspur on Saturday evening.