Saints U21 side went down to a 2-0 defeat against Sunderland, even missing a penalty in the process.
Saints were knocked off the top of the U21 Premier League after Sunderland defeated them 2-0 at Staplewood to leapfrog Reading and Saints to go top themselves after the first six games of the season.
Steven Caulker was the only truly experienced player in the Saints side although several others had some limited first team experience.
Despite a strong start from Saints it was the visitors who took the lead on 12 minutes, although Saints had several good chances afterwards to get back on level terms before Sunderland doubled their lead in the 42nd minute from the penalty spot.
On 53 minutes Ryan Seager failed to convert after Saints won a penalty of their own and there would be no more scoring in the game, although it was not for a lack of trying by Saints.
But the visitors stood firm and took not only the points but the top spot in the U21 Premier League.