Leeds United striker Kemar Roofe scored in the second half to seal a 1-0 victory over hosts Derby County in the first leg of their Championship playoff semi-final on Saturday.
Roofe, who had struck in both league clashes against Derby this season, collected a fine cross from winger Jack Harrison and tucked the ball past Derby goalkeeper Kelle Roos in the 55th minute to give his team a slender advantage in the tie.
"We've taken a good step as the first 90 minutes is done. You've seen all the drama and comebacks this week so we can't relax," Roofe told Sky Sports.
It was the 15th goal of the season for Roofe, who could have doubled his team's advantage, only to be denied by Roos as Leeds came alive following a sedate opening period.
Derby were awarded a penalty after Harrison appeared to foul Jayden Bogle in the 77th minute, only for referee Craig Pawson to overturn his decision and award a free kick to the visitors after consulting the linesman.
"I knew that Jayden Bogle had come in behind me but I was surprised it was called a penalty. It's all about perspective but I was going for the ball, I had no intention to take him down," Harrison said.
Leeds held on as Derby struggled to create clear chances at home. The teams meet at Elland Road in Wednesday's second leg.
Aston Villa defeated West Bromwich Albion 2-1 in the first leg of the other semi-final earlier on Saturday. The return leg is at The Hawthorns on Tuesday.
The finalists will meet at Wembley on May 27 to decide who will join Norwich City and Sheffield United in the Premier League next season.