Sammy Lee looks set to join the Saints coaching staff.
Brighton appear to have made the announcement ahead of Saints, after confirming that 55-year-old Lee would not become Sami Hyypia’s new assistant manager, despite them having previously said he would start work with them tomorrow.
Instead, he will join Saints as part of Ronald Koeman’s back room staff.
Brighton chief executive Paul Barber said: "It is extremely disappointing for the club, Sami Hyypia and those of us who worked hard to bring him here, that Sammy Lee has now reversed his decision after agreeing to become assistant manager.
"Nobody at our club or Bolton Wanderers, was aware of any interest from Southampton until several hours after we announced Sammy's appointment as our assistant manager. It's certainly not a situation any of us have come across before.
"Having already agreed his contract and terms with us to start work on Monday, we could have insisted on Sammy serving a notice period, but we all feel it would have been counterproductive to do so; and while it's incredibly frustrating for us we wish Sammy well.
"Our focus now is on working with Sami to help him recruit his assistant - while also supporting him to bring in the players he needs to improve the squad for the new season."
Lee added: "I was thrilled to be offered the job at Brighton and I was excited at the prospect of working with Sami Hyypia again - but, totally unexpectedly, I have been given an opportunity to work in the Premier League.
"I fully appreciate that this is not an ideal set of circumstances and I am very sorry for the inconvenience and any embarrassment my change of mind, after the announcement was made, has caused. However, at this stage of my coaching career, the opportunity to work again at the very top level of English football was not something I felt I could turn down.
"I hope that everyone at Brighton - including Tony Bloom, Sami Hyypia, Paul Barber and David Burke - and the club's fans can understand the difficult predicament I found myself in and why I made this decision.
"I would like to thank Tony, Sami, Paul and David for the opportunity to join Brighton and I genuinely wish them, the club and the fans the very best for the season ahead."
Lee was a much decorated player for Liverpool and even played a couple of games for Saints during a short spell at the club in the 1989/90 season.
He spent many years as a coach with Liverpool before leaving to become part of the England set-up.
Lee moved to Bolton to be assistant to Sam Allardyce before briefly taking the top job there, before rejoining Liverpool, and latterly Bolton again.
He joins Koeman’s staff that already includes his brother Erwin and Jan Kluitenberg and brings plenty of experience and knowledge of the English game with him.