"This is just the missing piece that everybody is keen to resolve," Southgate said. "All of the big clubs, whenever I visit them, are wrestling with this issue. If a lot of those players had a couple of years of first-team experience, it is a lot easier for their first-team manager to select them. But that is a conundrum we have got to solve."
The research is puncturing the mood of optimism around the England team after the Three Lions reached the World Cup semifinals for the first time in 28 years and qualified for the final four tournament of the inaugural UEFA Nations League in June 2019.
"What's clear is that we can't allow the trend to continue as it is because at what point do we stop?" Southgate wondered after Monday's Nations League draw. "Everybody saw the impact and the success of the national team in the summer and I think it is now prerogative that, while we still want a competitive Premier League that brings a lot of focus into our country as well, it's just trying to find this missing piece of development for English football."
Through 14 rounds of the Premier League, the average number of English starters is 29 percent — down from 33 percent across the last 38-game season. "It is incredible," Southgate said. "Nobody can tell me that if players are good enough, they will come through. That is not true. There are plenty of players who are good enough."
There has been success in the youth ranks. England won the Under-17 and Under-20 World Cups in 2017. Few of those players can be found in Premier League starting lineups "The quality of our academy system is very high," Southgate said. "So I know that around the country lots of people in youth development are really keen to get together and find a solution to that 17-21 age bracket and how we get those players playing.
"Although we are in a position where we can lead some of those discussions, it is not a case that the clubs are not on the same page with that. They are very much looking at how to bridge that gap as well."
Jadon Sancho had to leave Manchester City for Borussia Dortmund in the Bundesliga in 2017 in search of first-time opportunities. It paid off, as he earned a debut for Southgate's England senior squad in October, a year after scoring three goals at the U17 World Cup.
"For England, young people brave enough to travel, it's good for their development, for their maturity," Southgate said. "That's definitely something that people have noted and it will happen more and more."
Maybe not, though, after Britain leaves the European Union, which is due to happen in March. Brexit is set to end the free movement of players across Europe and prevent Premier League clubs being allowed the pick of continental talent from the ages of 16 to 18.
Southgate's bosses at the English Football Association are trying to to introduce post-Brexit quotas where Premier league clubs could include only 13 non-homegrown players in 25-man squads in return for scrapping the work permit system currently applied to non-European recruits.
Premier League clubs don't want any such restrictions. Being the world's richest league, the stakes are even higher to stay in the competition. Southgate was relegated with Middlesbrough in 2009 in his only Premier League job before climbing through the ranks coaching England.
"When you are a senior manager you need evidence sometimes to convince you that (young players) are ready to take the next step," Southgate said. "When the position of so many managers is precarious, and there isn't long-term stability, I can understand why they are loathe to risk."
National coaches get little time with their players. After victories over the United States and Croatia last month, England doesn't play again until 2020 European Championship qualifying starts in March.
"You don't get many opportunities at international level to actually win something, and we are trying to develop a winning mentality," Southgate said. "We've done that with our younger teams and we are trying to implement that into those players in terms of belief and we are now trying to build that with the senior players. This would be a step in the right direction, and start to knock down the barriers that remain."
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