Nottingham Forest 2 Leeds United 0
Leeds' promotion hopes suffered another blow with a 2-0 Sky Bet Championship defeat at Nottingham Forest.
Sammy Ameobi gave Forest a half-time lead before Tyler Walker wrapped it up in added time to move Forest to within a point of their second-placed opponents.
Faltering Leeds have won just one of their last nine Championship games and are now level on points with Fulham.
It was a deserved victory for the home side, who knocked Marcelo Bielsa's team out of their usual passing stride with their high-tempo pressing game.
Ameobi opened the scoring in the 31st minute with a powerful shot that should have been saved at his near post by Leeds goalkeeper Kiko Casilla.
Forest should have wrapped the game up nine minutes into the second half when Lewis Grabban fired at Casilla with the goal gaping.
However, Walker made the points secure from close range after Jack Harrison was caught napping.
Leeds, who were 11 points clear of third place earlier in the season, had to wait until 75 minutes to get a shot on target when Liam Cooper headed straight at Brice Samba.
Forest enjoyed a fast start with Grabban scuffing an effort wide in the seventh minute, before Tiago Silva had a long range effort saved by Casilla three minutes later.
Referee Oliver Langford waved away strong shouts for a home penalty after Cooper appeared to tug back Joe Worrall following a corner.
Silva was again thwarted by the Leeds shot-stopper with another long-range effort in the 13th minute as Forest stepped up the pressure.
Patrick Bamford made a mess of a header from a Pablo Hernandez cross, before Ezgjan Alioski had a shot deflected out for a corner.
Ameobi fired Forest when he beat Casilla at his near post, extending Leeds' unwanted record of having gone behind in every game since December 14.
Hernandez had a shot easily blocked on the stroke of half-time as the visitors continued to look flat up front, before Grabban missed his sitter - shooting straight at a prone Casilla after Forest had caught Leeds on the counter-attack.
Silva had a shot well-blocked by Ben White as he looked to guide the ball into the bottom corner in the 64th minute.
An unmarked Copper directed a powerful header straight at the keeper from a 75th minute corner, before the Forest keeper palmed the loose ball away on the goal-line.
Walker wrapped up the win in the fourth minute of stoppage time, tapping in after Joe Lolley had set him up after robbing Harrison of the ball.