Southgate also opened the door for a recall for Tottenham's Dele Alli who has missed the last two squads despite being one of the stars of the last World Cup campaign.
He said: “You know, we're still looking at Foden and thinking that it's a case of when, rather than if, unless something goes wildly off-track for him.
“So, there are some very good players, talented players that weren't in this squad. Obviously, guys that have been with us before like Dele as well. We have got incredible competition for places, particularly in those attacking five positions.
“And form and performances with club - we can't select on just the international games because there aren't enough of them and the level of the opposition has been at a certain level. We've got to see who are our best players to be able to play against those top teams."