SAINTS under-21s head coach Adam Asghar revealed he had to make three half-time substitutions against Celtic for "positive reasons".
The hosts were 1-0 up at the interval thanks to debutant Thierry Rohart-Brown in their final match of the Premier League International Cup.
However, after a triple-change saw Sam Amo-Ameyaw, Tyler Dibling, and Jayden Meghoma removed, the Hoops went on to win 3-1.
It means Asghar's side exit the competition winless - but Southampton's academy starlets could be in for another first-team chance.
Russell Martin takes his senior team to Watford in the FA Cup fourth round on Sunday, with all three involved last time against Walsall.
Asghar told the Daily Echo: "The International Cup is a great competition and we want a strong league finish to qualify next year.
"It was a bit scrappy and conditions played a part but we were a little bit naive and didn't exploit the spaces we talked about before the game.
"We scored a fantastic goal through Thierry and a great ball from Cam Bragg but we had three prescribed changes we had to make," he added.
"Hopefully, those changes are for positive reasons - but we knew the second half would be a big challenge and we had boys out of position.
"The goals we lost were avoidable and need to be improved on but I was prepared for the disruption in the second half after the changes."
Saints fielded a young side again with 15 year old Alejandro Gomes Rodriguez starting his second match at under-21 level.
Summer signing Rohart-Brown was making his first appearance while Jayden Moore, 17, has become a regular fixture at the back.
Right place, right time on #SaintsFCU21s debut 👏
— Southampton FC (@SouthamptonFC) January 24, 2024
✨ 16-year-old Thierry Rohart-Brown ✨ pic.twitter.com/sVlWavz4py
Harrison Miles, also 15, missed out through illness - while the likes of Amo-Ameyaw, Meghoma and Dibling are all 17.
Asghar insisted: "It is all earned on merit. We had planned to use Thierry in a game in December but he picked up an injury.
"He has done so well since he came into the club from Reading and again on his first outing.
"All of the lads who have come up have added to the team so we must keep challenging them to make sure they develop."
The fixture came in the wake of Kami Doyle's medical at Premier League outfit Brighton & Hove Albion.
The 18 year old midfielder, a star in the under-21s team before suffering an injury in October, is set to depart the club after 10 years.
Asghar explained: "It is always going to happen at this level.
"It depends on what certain players want or what they feel they need and you can debate whether they are right or wrong decisions.
"I never had the fortune of working with Kami because he was injured from day one when I arrived.
"In my dealings with him, he has been a good young man and I wish him all the best with the decision he has made."
Saints have already made an addition in the attacking midfield with the signing of Cork City's Joe O'Brien-Whitmarsh, confirmed earlier this month.
The 18 year old Irishman - a regular in League of Ireland - could be named in the Premier League 2 squad to face Leicester City on Monday.
"We had a look at Joe before Christmas in a couple of days of training," Asghar said.
"He impressed and he has already played a lot of first-team football for his age. He is a mature young man from the conversations I have had.
"He will take a bit of time to get up to speed due to his season finishing but we will build him up and he is training with the group.
"Hopefully, we can get him involved on Monday - the boys have really taken to him and we are looking forward to working with him."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here