Koeman said when he was there that none of their academy were ready. A numb nuts assessment immediately proven wrong when his successor went in there.
Since he left, Sims, McQueen and Olomola have all gained a first team footing.
Here's a good article on what Puel was asked to do to unravel the harm done to the Southampton youth policy when he was there.
http://www.fourfourtwo.com/sg/news/puel-i-replaced-koeman-give-southampton-youngsters-a-chance
It's not even up as serious debate that Koeman tried to have their home grown system placed in mothballs when he was there because he wanted to spend cash. Only now are they recovering from his purblind attitude.