Gareth Southgate has warned the members of England's disappointing European Under-21 Championship campaign this summer that they have no guarantee of stepping up into his senior side.
Aidy Boothroyd saw his Young Lions take just one point from three Group C games as they put in their worst tournament performance since 2013.
England suffered defeats to France and Romania before losing the lead three times to draw their final match with Croatia.
Southgate has been keen to promote youngsters into the England team since he took charge, a trend that continued when he announced his 25-man squad on Thursday for the upcoming Euro 2020 qualifiers against Bulgaria and Kosovo.
Kyle Walker was omitted as Aaron Wan-Bissaka was handed his first call-up, with uncapped duo Mason Mount and James Maddison also included.
The trio were all part of the underwhelming Under-21 tournament and will now be looking to retain a place in the senior set-up but Southgate says others should not take progression as a given.
"I don't think we've picked any of the under-21's squad purely on the tournament in the summer," he said.
"They won't get in just because they're young. You know, I've felt some of the young ones in the summer were kind of: 'Well, we're done with the under-21s now and the next step is the seniors, because that's what happened last time.'
"That's not what happens. They've got to play well and it's going to be harder to get it, because you can see the players we've had to leave out, between fitness, who've got a lot of caps between them, high-level players.
"We know there are some others around the fringes that could be close. And we know that there are some more young ones coming that are going to push that as well.
"So that challenge is there for all of them. And whether they are younger or older don't assume anything, because I think everyone has to keep performing if we're to challenge the best teams and that's how we are going to develop."
England's Euro Under-21 tournament began with defeat to Italy before a humbling 4-2 loss to Romania – after which goalkeeper Dean Henderson, who made an error during the game, insisted: "We wanted to come here and win this tournament...Whoever goes on to win the tournament realistically we know we can beat as well."
Southgate believes such confidence can sometimes be put down to a lack of experience and that humility can often be as important as ability.
"That's a little bit down to their age. They've got to recognise it and learn from it," he added.
"That's the age of that group, you've got to go through some of those set-back periods. For me, the biggest reminder which was in the seniors was that we must always have humility.
"And we play a country like Romania, I don't know if we thought we were better but they had some really good players. Some of them have moved already, the boy's doing really good at Reading, (George) Puscas.
"I thought they were a good team, they had a stadium full of support. I didn't like the fact that our boys came off that and thought they were still the best team in the tournament. That can't be the case."
