Jack Ross deployed a 3-5-2 system in the Checkatrade Trophy win over Notts County, with Bali Mumba in the unusual role of right-wing back.
And his manager says it is testament to the 17-year-old’s character and skill that he adapted so well to the role.
Mumba, who signed his first professional contract earlier this season, had a challenging start against Notts County.
But he grew into the role and played an important part as Sunderland ran out 2-0 winners, thanks to a Dan Jones own goal and a Jerome Sinclair penalty.
Ross made eight changes and changed his system for the Checkatrade Trophy last 32 round.
On Mumba’s performance, Ross said: “It was really interesting because’s he’s played as a full-back when he was younger and he played as a full-back with England when he was away with the under 18s.
“But wing-back is slightly different again and the first half was challenging for him.
“Playing against a decent player, physically strong and the full-back was strong too.
“But I thought second half he was really good, and that’s testament not just to his ability but his character.
“As a 17-year-old, to have a tricky first half, he did some good things, but to show what he did in the second half... he’s a good player and I’m really pleased with him.
“Taking into account everything we’ve asked of him and playing in a strange position, I couldn’t ask any more of him,” added Ross.
The draw for the next round of the competition is made later this week, with the last 16 round regionalised still.
Sunderland are now just three wins from a Wembley final and the Black Cats extended their unbeaten run to 16 games in all competitions.
Sunderland return to League One action on Saturday away to Accrington Stanley.