The Black Cats boss named just one 'qualifying' first-team player by the competition’s rules as Denver Hume captained the side.
Hume has just recovered from a hamstring injury and needs game time, yet Johnson resisted the temptation to play any other senior players.
Sunderland’s youngsters made a positive impression, though, as Tyrese Dyce put his side ahead in the second half at the Stadium of Light.
United drew level after an excellent strike from Zidane Iqbel, yet Stephen Wearne’s header secured the win for the hosts.
Following last week’s 2-1 win at Lincoln, Sunderland have qualified from Northern Group F with a game to spare, against League Two side Bradford.
Our chief SAFC writer Phil Smith has delivered his verdict on how each player fared against United’s under-21s side.
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Sunderland’s youngsters made a positive impression, though, as Tyrese Dyce put his side ahead in the second half at the Stadium of Light.