The Three Lions were only able to pick the up a solitary victory over Qatar in their first visit to southern France in nine years, with defensive errors leading to all five of the goals they conceded.
But former Middlesbrough boss Southgate believes taking part has proved a worthwhile exercise for his squad despite some disappointing results.
"Ultimately we are looking at players who can go into our first team and be a success with the seniors. There is no doubt that this week there are several I know who can go and do that," he told BT Sport.
"We needed that challenge of playing against some top nations to be able to see if they can cope with that. Quite clearly they can.
"I would have to say results-wise we haven't got what we have deserved, but the two games we have lost have been by the finest of margins."
Despite dominating against Portugal in Avignon, a defensive mix-up between Saido Berahino and Liam Moore meant the competition ended in frustrating fashion for Southgate's side.
And the 43-year-old admitted that the way in which the match went was in keeping with the way his side had thrown away matches throughout the tournament.
"I've got to be pleased with the performance. We've played against a top side and we've more than matched them.
"They had slightly the better of it in the first half without really creating anything clear-cut. We created good chances of our own and then in the second half we were dominating the game and conceded a quite incredible goal.
"That's summed up our tournament. The players have been a credit to work with and I though today was our best performance. We passed the ball well to Portugal up and I'm disappointed for them because they deserved more out of the game."