The Saints copped two-goals in either half in front of their home fans and their Argentine manager was bereft of excuses.
"It wasn't our best game, for sure," said Pellegrino. "The only positive thing is that it was a friendly game.
"We can make a lot of conclusions. We tried to move all the players – some of them were playing just their first game, like Nathan or Ward-Prowse.
"We have to try to keep going and learn from today. It is a difficult game to analyse, because we want to do our best at home.
"But the best thing is that it was a friendly game – this is the best conclusion that we can make from today."