Southgate, who gave five players their international first-team debuts against Germany on Friday, has added goalkeeper Angus Gunn, defender Lewis Cook and striker Dominic Solanke to the squad for Tuesday's Wembley encounter with the five-times World Cup winners.
All three were in action on Friday for England's under-21 side in Ukraine -- and the latter two featured in the under-20s' World Cup-winning campaign earlier this year.
Manchester City's Gunn, 21, who is on loan at second-tier Norwich City, was called up to replace Jack Butland, who broke a finger in training.
Cook, of Bournemouth, and Liverpool's Solanke, both 20, join an already young squad hit by injuries to senior players, including Dele Alli and Harry Kane, and now without Manchester United defender Phil Jones, who limped off after less than half an hour of the Germany match with what England say is a thigh problem.
Harry Maguire, Ruben Loftus-Cheek and Tammy Abraham all made their senior debuts on Friday and were joined by two more debutants -- substitutes Joe Gomez and Jack Cork -- during the game.
The starting 11 had just 101 caps between them -- their most inexperienced side since 1980.
(Reporting by Neville Dalton, editing by Pritha Sarkar)
