Match ends, Derby County 0, Middlesbrough 1.
Patrick Bamford's 16th goal of the season earned Middlesbrough victory against promotion rivals Derby County.
The on-loan Chelsea forward scored for the third time in two games to stretch the Rams' winless run to five matches.
Bamford rounded goalkeeper Lee Grant to open the scoring against his old club from a narrow angle in the 64th minute.
Middlesbrough rise to second place after a fourth victory in six games, and are five points ahead of Steve McClaren's fifth-place Derby side.
Bamford, a Nottingham Forest supporter, spent time on loan at Derby last season.
The England Under-21s international looks more of a threat after being pushed into a central attacking role, and he sealed a deserved victory after finding the net from a Lee Tomlin pass.
Derby's form has deserted them at a crucial point in the season.
They again missed their injured 19-goal top scorer Chris Martin as they suffered a defeat that leaves them with two wins from 10 games.
It brings added pressure as they prepare to visit play-off-chasing Wolverhampton Wanderers on Friday.
Middlesbrough, who travel to third-placed Bournemouth on Saturday, could have won more comfortably.
Striker Jelle Vossen's first-half lob struck the inside of a post, and they had a late penalty claim turned down when Bamford went down under a challenge from defender Richard Keogh.
They held out for a vital win that leaves them behind leaders Watford on goal difference.
Derby manager Steve McClaren:
"That is the sort of quality that Patrick Bamford is capable of producing and that was what made the difference.
"I was proud of the character my players showed but at the moment, with our injury problems, we can't produce the one special moment that settles games like this.
"We'll have our injured players back after the international break that is coming up and I have no doubt that we will come back strong.
"Nothing is settled by any means. There are eight games to go and believe me, there will be many a twist and turn to come in this division."
Middlesbrough boss Aitor Karanka:
"Nobody can be surprised by Patrick's goal. He has taken the main responsibility for scoring and he has the confidence to make the most of his chances.
"This was a very important win and I was very pleased with the spirit we produced for such a big test. Derby are one of the best sides but we gave them very few chances and came away with a big win.
"Now we face more tough games against Bournemouth, Watford and Norwich so we must continue to show the same character."
- 2ChristieBooked at 51minsSubstituted forThomasat 75'minutes
- 4BrysonBooked at 61mins
- 26HansonSubstituted forHendrickat 70'minutes
- 19HughesBooked at 57mins
- 10WardSubstituted forLingardat 70'minutes
- 8ClaytonBooked at 63mins
- 10TomlinSubstituted forReachat 86'minutesBooked at 90mins
- 21VossenBooked at 51minsSubstituted forForshawat 81'minutes
- 27AdomahSubstituted forNsueat 90+1'minutes
- Andy D'Urso
- Shots on Target
Second Half ends, Derby County 0, Middlesbrough 1.
Attempt saved. Jesse Lingard (Derby County) header from the centre of the box is saved in the centre of the goal. Assisted by Raúl Albentosa.
Corner, Middlesbrough. Conceded by Richard Keogh.
Attempt blocked. Patrick Bamford (Middlesbrough) left footed shot from the centre of the box is blocked. Assisted by Adam Clayton.
Adam Reach (Middlesbrough) is shown the yellow card for a bad foul.
Jeff Hendrick (Derby County) wins a free kick in the defensive half.
Foul by Adam Reach (Middlesbrough).
Attempt missed. Raúl Albentosa (Derby County) right footed shot from outside the box is close, but misses to the right.
Attempt blocked. Richard Keogh (Derby County) right footed shot from outside the box is blocked. Assisted by Raúl Albentosa with a headed pass.
Substitution, Middlesbrough. Emilio Nsue Lopez replaces Albert Adomah.
Richard Keogh (Derby County) wins a free kick in the attacking half.
Foul by Patrick Bamford (Middlesbrough).
Attempt saved. Johnny Russell (Derby County) left footed shot from the centre of the box is saved in the centre of the goal. Assisted by Jesse Lingard.
Substitution, Middlesbrough. Adam Reach replaces Lee Tomlin.
Attempt missed. Jesse Lingard (Derby County) right footed shot from the centre of the box misses to the left.
Kwame Thomas (Derby County) wins a free kick in the attacking half.
Foul by Jonathan Woodgate (Middlesbrough).
Substitution, Middlesbrough. Adam Forshaw replaces Jelle Vossen.
Attempt blocked. Tom Ince (Derby County) left footed shot from outside the box is blocked. Assisted by Jeff Hendrick.