Eddie Nketiah stepped off the bench to earn all three points for Leeds United in a 1-0 victory over Brentford in the Championship on Wednesday night.
Marcelo Bielsa made an enforced change for the visit of the Bees with Gjanni Alioski replacing the injured Barry Douglas.
The opening period got off to a slow start as both sides played a number of loose passes.
Brentford were posing more questions than their counterparts and almost took the lead as Bryan Mbeumo cut inside as the visitors broke into the Whites half.
The forward curled an effort on goal which smashed Kiko Casilla's upright with the stopper beaten.
United, though, responded as Patrick Bamford fired two headers wide of the mark from inside the box.
Adam Forshaw also saw an effort fly over the bar from the edge of the area with the two sides level at the interval.
United started the second half much the better side and could've had a penalty as Mateusz Klich fired a shot which appeared to strike a Brentford arm.
Referee Andy Davies waved away the protests as Stuart Dallas was booked for his complaints.
The Whites pushed on but were left frustrated as Bielsa opted to change things as Nketiah and Helder Costa stepped off the bench.
It was the latter who proved to be the architect 10 minutes from time as the former finished off a well worked move to set Elland Road alight on his home debut.
Klich released Costa down the flank before he squared to the Arsenal loanee who sealed all three points with an immediate impact.
Leeds United: Casilla, Alioski, White, Cooper, Dallas, Phillips, Klich, Harrison, Forshaw, Hernandez, Bamford. Subs: Meslier, Berardi, Shackleton, McCalmont, Bogusz, Costa, Nketiah.
Brentford: Raya; Pinnock, Jansson, Jeanvier; Dalsgaard, Jensen, Norgaard, Henry; Sergi Canós, Mbeumo, Watkins. Subs: Daniels, Thompson, Benrahma, Dasilva, Forss, Marcondes, Racic.
Referee: Andy Davies.