The trio were key protagonists in last summer's unparalleled talent drain from the Saints as they swapped the south coast for Merseyside at a reported combined cost of Â£49million.
Lallana, Lambert and Lovren have enjoyed differing levels of success since moving to Anfield and will receive receptions of varying warmth upon their first visit to Southampton since departing.
The spectre of those returns have understandably dominated the build-up to Sunday's match, but it is not something Koeman is interested in.
"It's not my question, my question is to prepare the team for the Sunday game," the Saints boss said
"I don't talk about players who are coming back to the club where they played last season, because then I can talk every week about a player who comes back to Southampton.
"Lallana is a very good player, doing well in Liverpool
He chose to change the club after a good opportunity and nothing else.
"It is Southampton against Liverpool, not Southampton against some players who played last season for Southampton."
Friday's pre-match press conference saw Koeman come closer than any time during his Saints reign to losing his cool as a journalist peppered him with questions about the returning triumvirate.
The Dutchman told the reporter to "ask me about Southampton" and, as he became increasingly irked, asked: "You're the agent of Lovren and Lallana? Why that kind of questions all the time?"
After eight questions on the subject, the head of media intervened in a bid to move matters onto Southampton's current squad.
"You think I am thinking about losing a game? No way," Koeman said
"I am thinking of winning the game
I am not negative thinking.
"I'm surprised they have four points less than we have and to come closer to us they have to win
If they don't win, they don't come closer."
Southampton's chances of keeping Liverpool at bay are boosted by the return of Morgan Schneiderlin, Shane Long and Matt Targett on Sunday.
There will still be a number of absentees at St Mary's, though, with the suspended Ryan Bertrand joining Toby Alderweireld, Emmanuel Mayuka and Jay Rodriguez on the sidelines.
The latter has not played for 321 days after rupturing an anterior cruciate ligament last season, with some talk of a March return.
"It's a long way now for Jay and if it happens in March we are very happy," Koeman said
"If it happens in April we will see but at the moment not because he needs more time."
Koeman had initially hoped Rodriguez's return would be like a January signing, but if time ticks on it may be more like a summer addition.
"I hope not," he said
"I hope that Jay can still play some games in this season, but it is all about the freshness and the shape of the player.
"We don't take any risk because the player is too good to take that risk.
"We know to handle injuries and problems because now I think for the first time I have players back after the last two or three months and that's good news."
Source : PA