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 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.
“It’s not my question, my question is to prepare the team for the Sunday game,” said Southampton manager Koeman.
“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.”
The 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?”