The 19-year-old, elevated to Eddie Howe’s first-team squad this season, is expected to feature when Cherries host Saints in a pre-season friendly tonight (7.45pm).
Cargill was released by Saints as a 12-year-old after being told they had a left-back ahead of him in the pecking order – Luke Shaw, whose £27m move to Manchester United last month was a world record fee for a teenager.
Invited to join the Cherries centre of excellence after impressing during a trial, Cargill, who almost quit the game following his rejection by Saints, progressed through the club’s youth set up and development squad and was rewarded with a two-and-a-half year contract in November.
Converted by boss Howe to a left-sided central defender, Cargill, who made his Football League debut during a loan spell at Torquay last season, turned in an accomplished display in the first half of Cherries’ 2-2 draw against FC Copenhagen a fortnight ago.
Cargill, who had a loan spell with AFC Totton in 2012/13, said: “It was a great experience to play a Champions League team. I was up against Steve De Ridder, who used to play for Southampton, and a striker called Andreas Cornelius, who joined Cardiff for £7.5m this time last year before going back to Copenhagen.
“I felt I did well and they didn’t threaten our goal in the first half.
“Hopefully, I will get some game time in our next few friendlies when we play both Southampton and Swansea. There is nobody you would rather face than Premier League opposition because it is the best league in the world. Playing against quality players pushes you to the maximum and helps you see where you are with your own game.
“If I do get a chance, I have to make sure I take it with both hands and do the best I can. I need to prove myself to the manager every day, both in training and in games.”
Howe has already stated he has no immediate plans to loan out Cargill and says the youngster could start the season as Cherries’ third-choice central defender behind Tommy Elphick and Steve Cook with Elliott Ward still on the road to recovery.