The pair were part of a mass Southampton exodus after Mauricio Pochettino departed for Tottenham in the close-season, with Rickie Lambert also moving to Liverpool while Luke Shaw joined Manchester United.
Ahead of the trio's first return to St Mary's, Koeman grew frustrated with discussion about Lovren and Lallana in his pre-match news conference.
After a number of questions about the pair, the Dutchman queried one journalist: "You are the agent of Lovren and Lallana?
"Maybe the team with Lovren was still stronger, but we did a great job to replace good players with good players.
"One of the qualites of our team is we only receive 17 goals and that's a very good record. That kind of numbers will make a good chance to a high position.
"I don't answer more questions about players of Liverpool, I don't know why you have come to this press conference to ask only questions about that. There's no way I'll come into what you'd like to hear about them.
"That's not my question, mine is to prepare the team.
"I don't talk about players who are coming back to the club where they play last season because I would be talking every week about a player coming back to Southampton.
"Lallana is a very good player and is doing very well at Liverpool, he chose to change club after a good opportunity and nothing else. It's Southampton against Liverpool not Southampton against some players who played last season for Southampton."
