A goal in either half condemned Derby County to a 2-0 defeat away at Middlesbrough on an afternoon where Steve McClaren’s side finished with 10 men.
Patrick Bamford opened the scoring after just six minutes after Boro profited from wasteful play and it set the tone for the remainder of the contest.
Ryan Shotton was sent off just after the hour mark after he had hauled down Bamford in the area and Grant Leadbitter slammed in the resulting penalty as Derby slipped off the top of the Sky Bet Championship for the first time in five weeks.
Despite making a bright start to the game, Derby were soon on the back foot as a stray pass from Richard Keogh was intercepted in the middle of the park.
Karanka’s side moved through the gears and spread the the ball quickly out to the left to Adam Reach, who slipped a low pass into the feet of Bamford whose first time shot clipped the far post and into the back of the net.
With Boro willing to sit back, Derby continued to boss the possession statistics and could have equalised just two minutes later.
A neat move from the Rams forced a corner on the left hand side and Craig Bryson’s inswinging cross was headed narrowly wide by the towering Shotton.
After a spell where chances came at a premium, Lee Grant was called upon to make a final double save to prevent the home side from doubling their lead.
The first came from Bamford who raced away from Keogh and rifled a drive at the ‘keeper’s palms, before Grant recovered to tip over Jelle Vossen’s follow up for a corner.
Reach blazed over with 10 minutes of the half remaining and Derby’s only effort on goal up to the 37th minute was a tame first time effort from Johnny Russell that went well wide of Dimi Konstantopoulos’ goal.
Another stray pass from Derby gifted Middlesbrough the chance to test Grant as Emilio Nsue’s low drive took a deflection into the arms of the Derby goalkeeper, before a stray pass at the opposite end of the pitch gave the visitors the chance to get back into the contest on the brink of half time.
After Russell collected a loose ball on the right, the forward cut inside and fed the ball to Hendrick who set himself and hit a first time curling effort tamely into the arms of Konstantopoulos.
It proved to be the last of the first half action and McClaren signalled his discontent with his side’s display by opting to make two changes during the interval.
Leon Best and Jordon Ibe came on in place of Omar Mascarell and Simon Dawkins, which also altered the Rams’ formation to a 4-4-2 for the beginning of the second 45 minutes.
Boro continued to create the better openings as Reach headed over after connecting with a cross from the right and a poor clearance from Shotton cannoned off Bamford and narrowly wide.
Grant’s poor pass out gifted the home side another chance as they began to pile the pressure on Derby’s backline.
After a number of last ditch tackles, Bamford fired an effort into the ‘keeper’s midriff and George Friend’s drilled cross into the six-yard box narrowly evaded everyone in the box as the contest approached the hour mark.
Moments later, Leadbitter’s deep free kick evaded everyone in the area and forced Grant into another fine save before Adam Clayton drilled a fierce effort wide from 25-yards from the follow up.
The inevitable, though, came and Derby found themselves two goals down and reduced to 10 men after 63 minutes.
A slipped ball through to Bamford from Albert Adomah found the striker bearing down on Grant’s goal and Shotton hauled the on-loan Chelsea striker down in the area, leaving referee, Roger East, with no choice but to the send the defender off.
Up stepped Leadbitter to fire the spot kick beyond Grant to score his tenth goal of the season and leave Derby with a mountain to climb.
Whilst holding Derby at arms length, Boro, with their one-man advantage, continued to create the better chances. Bamford forced Grant into another fine save and substitute Wildschut had a teasing cross turned away for a corner after waltzing inside Russell and then Christie.
With four minutes remaining, Derby were presented their first clear cut opportunity to half the deficit as Martin laid the ball into the path of Bryson, whose firm shot was beaten away by Konstantopoulos.
That was how it remained as Derby’s time at the top of the Sky Bet Championship came to an end for the first time in over a month.
Middlesbrough: Dimi, Nsue, Gibson, Ayala, Friend, Reach, Clayton, Leadbitter, Adomah, Vossen (Wildschut, 77), Bamford (Kike, 74)
Substitutes not used: Mejias, Husband, Whitehead, Omeruo, Veljkovic
Derby County: Grant; Christie, Keogh, Shotton, Forsyth; Mascarell (Best, 45), Hendrick (Hughes, 60), Bryson; Russell, Dawkins (Ibe, 45), Martin
Substitutes not used: Roos, Buxton, Coutts, Calero