The 16-year-old was the hero for Leeds United's Under-23 side.
Leeds beat their Barnsley counterparts 1-0 at Thorp Arch for a second successive victory in the Professional Development League.
The hero was the 16-year-old full-back, who tucked home a rebound after Romario Vieira's initial strike was parried away by the opposition goalkeeper.
Downing won Apprentice of the Year for Leeds back in May - an award previously given to Sam Byram - and Blunt admits he's delighted for the teenager.
He told LUTV: "Extremely pleased at the end - especially again when we had so many youngsters; we finished with four Under-18s.
“Extremely pleased for Matty Downing, probably the first goal he's ever scored and he came up with the winner.”
Blunt's side are sixth in the Development League and the win over their Yorkshire rivals was Leeds' second in succession, having previously beaten Huddersfield Town 3-2.
If Downing develops into a player anywhere near the quality of Byram - who joined West Ham United last January - then the Whites have another fine talent on their hands.
The Yorkshire club have a promising future in the full-back roles, it would seem. Behind left-back Charlie Taylor is Taylor Denton, while right-back Lewie Coyle has been banging on the door for a while.
General view inside the stadium before the game - Elland Road