Eddie Nketiah made a name for himself at Elland Road by coming off the bench and scoring a late winner as Leeds returned to the top of the Championship with a 1-0 victory over Brentford.
With former Arsenal striker Ian Wright watching on from the stands, the Gunners loanee was sent on for his Championship debut in the 77th minute in a bid to find a goal.
Just four minutes later, the 20-year-old tapped home from Helder Costa's cross to ensure Leeds leapfrogged Sheffield Wednesday to the summit.
Former United defender Pontus Jansson appeared to be helping his new side to a point on his return to the stadium where he made his name in English football.
A fans' favourite at the Whites, the Swede's departure to the Bees for just £5.5m this summer baffled many of the home supporters.
Jansson was the subject of occasional boos and chants of 'You're Leeds and you know you are', but could not prevent Nketiah's winner.
England U21 boss Aidy Boothroyd, plus cricketers Chris Woakes, Jonny Bairstow and Jack Leach were among the spectators as Jansson lined up against his former side.
Brentford had the first effort on target as Sergi Canos tamely shot at Kiko Casilla following smart link-up play with Ollie Watkins.
Leeds made a sloppy start, struggling to find their usual fluency, and Brentford were a post away from breaking the deadlock in the 24th minute.
Bryan Mbeumo let fly with a left-footed strike from 25 yards that beat Casilla but cannoned off the woodwork.
The hosts responded by racing down the other end and Mateusz Klich tested goalkeeper David Raya with a low left-footed volley.
A stretching Patrick Bamford headed over the top and then, having beaten the on-rushing Raya to the ball, nodded just wide of the empty net.
Former Brentford midfielder Adam Forshaw ended the first half by skewing a header wide and started the second with a rasping drive that Raya held.
Leeds looked a different team after the interval, pinning Brentford in their own half, with Pablo Hernandez's powerful effort just flying over the top.
Elland Road was crying for a penalty in the 64th minute when a Klich shot hit a Brentford player on the arm in the box, but referee Andy Davies was unmoved.
Leeds were always susceptible on the counter attack and the warning signs were there when Watkins curled wide.
But Marcelo Bielsa introduced Costa and Nketiah, with the pair combining to devastating effect nine minutes from time to raise the roof.
The managers
Marcelo Bielsa: "I think we deserved to win the game, we dominated the game. We didn't create a lot of goal chances, but enough chances to make a difference. It was a physical and demanding game and the best moment we took.
"It was lucky (the substitutions) because only sometimes these things can happen, because the skill of the coaches is not making the decision of the players who make the last pass or score the goal."
Thomas Frank: "We know Elland Road is always a difficult place to play, especially with Bielsa and the way they press, not only high intensity but the different way of doing it.. First half I think we play a top away performance, pressing high and causing Leeds problems, having good opportunities. An even game.
"Second half, for whatever reason, they stepped up and we couldn't keep the level of intensity. We lost the ball too easy and didn't run at them as much as we did in the first half. Defensively, it was a top defensive performance, but for one moment."