
The 27 year old is expected to depart St Mary's by 11pm next Tuesday, after being left out of the squad altogether for the two most recent fixtures.
Brereton Diaz started the first round of the Carabao Cup at Colchester United, and he was a late substitute at Watford in the Championship opener.
But he was not named amongst the bench for games against Stoke City and West Ham, with Saints beaten 4-1 by the Hammers on Tuesday night.
Chile international Brereton Diaz was signed for £7million in 2024 but has failed to score or assist in 17 Saints appearances, and looks set for an exit.
"There are some conversations and negotiations taking place at the moment, and I would expect there to be some news," Eckert told the Daily Echo.
"You can look at the squad, and you see who's involved and who's not. It's not a secret that there's still going to be some movement over the next days."
Brereton Diaz was loaned out to former club Sheffield United in January 2025, and then spent last season on loan at Championship rivals Derby County.
Both clubs have been linked with a potential summer return for the forward, with Derby most recently and strongly linked to signing him once again.
Defender Mads Roerslev is another who could make a surprise exit before the end of the window, with Eckert opening the door to his departure.
Mads Roerslev could depart Saints in the next week (Image: Southampton FC)
The Danish international, who signed for the club last year on a four-year deal from Brentford with Premier League pedigree, has not played for Eckert.
Roerslev missed the second half of last season with an Achilles injury, but after playing during pre-season, he has not made a single competitive squad.
Eckert said: "I think that James [Bree] played almost every single game last year. I have big trust in James, and it's just a normal conversation.
"If you are out injured for almost a year, what is the best way to find rhythm again? At the moment, it's clear that James is our number one.
"We'll see what we do over the next days. Let's see what the next days bring."
Aaron Ramsdale, Gavin Bazunu, Yuki Sugawara and Damion Downs remain out of Eckert's plans and are attracting interest for moves elsewhere.
Saints are looking to add a centre-midfielder to their squad ahead of the deadline, following the sale of Shea Charles to Fulham for up to £30m.
"We're having conversations. I think we know that we need to do something, and I'm sure that we will get something done," Eckert insisted.