Kemar Roofe scored the only goal of the game as Leeds took a huge step towards the Championship play-off final with victory over Derby.
The Whites striker was in the right place to slot home Jack Harrison’s superb cross shortly after half-time and give the away side a precious lead.
Derby thought they had a way back into the match when referee Craig Pawson awarded a penalty for a foul by Harrison on Jayden Bogle, but the decision was overturned by the assistant referee.
The second leg takes place at Elland Road on Wednesday with a spot in the final against either West Brom or Aston Villa at stake.
Express Sport have rated how the Leeds players performed against Derby, but do you agree?
Leeds United player ratings vs Derby County – Championship play-off semi-final
GK: Kiko Casilla – 7
Sharply off his line on a couple of occasions and solid under the high ball, although the Spaniard’s shot-stopping wasn’t tested as Derby failed to register a shot on target.
RB: Luke Ayling – 6
Solid enough at right-back as the Leeds rearguard restricted Derby to pot-shots from distance.
Didn’t get forward as much as he usually likes to, but Whites fans won’t have minded in such a cagey affair.
CB: Gaetano Berardi – 7
Brilliant covering early on snuffed out danger when David Nugent threatened as the Italian stepped up in place of the injured Pontus Jansson.
Went in the book for bringing down Tom Lawrence but looked composed otherwise.
CB: Liam Cooper – 7
Solid for much of the afternoon, although he had his heart in his mouth when he brought down Harry Wilson on the edge of the area.
Sensible with his distribution as Leeds dominated possession.
LB: Stuart Dallas – 7
Went close with a couple of first-half drives and carried out his defensive duties diligently.
CM: Kalvin Phillips – 6
Engaged in a running battle with Duane Holmes as he helped Leeds gain a foothold in midfield.
One shocking first-half effort went out for a throw.
RM: Pablo Hernandez – 6
Great footwork always kept the Derby defenders on their toes but the Leeds playmaker missed his best chance of the match when he swung at thin air with the goal at his mercy.
CM: Adam Forshaw – 4
Started with plenty of purpose running from deep but went down injured after just 24 minutes.
CM: Mateusz Klich – 5
Got through plenty of work in the engine room and ruffled Derby feathers with his combative nature, although the midfielder could have seen red for leading with his head against Fikayo Tomori.
LM: Jack Harrison – 7
Provided a moment of real quality with his delivery for the goal as he started the second half brightly.
Survived a controversial penalty appeal after tangling with Omar Bogle.
ST: Kemar Roofe – 8
Started slowly but built up a head of steam with some excellent hold-up play and was rewarded when he was in the right place to tuck home Harrison’s cross.
A constant threat with his movement and was the difference for his side.
SUB: Jamie Shackleton (on for Forshaw, 24 mins) – 6
Thrown into the action early with Forshaw injured and rose to the occasion well.
Almost got on the scoresheet when he tested Kelle Roos late on.
SUB: Jack Clarke (on for Roofe, 80 mins) – N/A
Little time to make an impact.