Leeds beat 10-man Sheffield Wednesday thanks to a David Healy penalty.
On-loan goalkeeper Brad Jones was sent off for bringing down Healy, who got up to place a precise shot past substitute keeper Chris Adamson.
Leeds were the better side after the break, but the Owls, with better luck, might have been ahead at half-time.
Deon Burton missed two good chances, Chris Brunt had a free-kick that was well saved by Tony Warner, while Lloyd Sam hit the post from a cross.
The dismissal of Jones marked an unhappy day for Middlesbrough goalkeepers.
Jones and David Knight, on loan from Boro to Oldham, were both sent off on the same afternoon.
Sheffield Wednesday manager Paul Sturrock:
"I wanted this year to show we are a hardened Championship team and I think we're getting there.
"We had a kick in the teeth today but I was very pleased with their attitude, commitment and thoughtfulness.
"We could have gone up to the giddy heights of eighth if we'd have won and that would have been nice."
Leeds manager Kevin Blackwell:
"It was a clear penalty.
"The minute the keeper goes to ground he is asking for trouble.
"We had some great chances, we've put in a solid performance and we deserved to win.
Sheff Wed: Jones, Coughlan, Simek, Bougherra, Spurr, Hills (Adamson 68), Whelan, O'Brien, Brunt (Lunt 82), Sam (Bullen 76), Burton.
Subs Not Used: McClements, McAllister.
Sent Off: Jones (67).
Booked: Sam, Lunt, Bullen.
Leeds: Warner, Kelly, Crainey, Butler, Kilgallon, Westlake, Lewis, Carole (Foxe 81), Derry, Healy, Moore.
Subs Not Used: Sullivan, Richardson, Blake, Beckford.
Goals: Healy 70 pen.
Ref: S Bennett (Kent).