Middlesbrough dropped out of the Championship automatic promotion spots after Bobby Clark stunned the Teessiders with a second-half winner for Derby County.
It took a string of saves from Jacob Widell Zetterstrom to give the Rams hope of upstaging Boro, with the Sweden international denying Hayden Hackney, Tommy Conway and Delano Burgzorg either side the break.
While Sol Brynn did well to keep Patrick Agyemang out early in the second half, RB Salzburg loanee Clark earned the Rams a hard-earned victory with a composed finish to leave Boro winless in four games.
Kim Hellberg’s side have failed to score in all four of those games, losing three, to slip to third in the table and fall nine points behind leaders Coventry City.
Derby ended their own three-match winless run with what was only their second victory in eight games to move to within five points of the play-off spots.
A combination of fine work from Rams keeper Zetterstrom and poor finishing stopped Boro from taking an early lead.
The Swede rushed off his line to keep Hackney out with a sprawling save before Conway squandered a huge chance moments later, failing to connect with his attempted shot after Callum Brittain teed him up with an inviting ball into the box.
Conway did better the next time Brittain found him lurking in the penalty box, but Zetterstrom was equal to the striker’s side-footed volley to keep scores level.
It took until the final minute of the first half for Derby to call Brynn into action at the other end, with a curled free-kick from Joe Ward forcing him into a save at his near post.
And after Zetterstrom started the second half with another crucial save from Burgzorg, Brynn came up with the best of the afternoon to deny Patrick Agyemang from a tight angle.
The visiting keeper, however, was left exposed when former Liverpool midfielder Clark got to the ball ahead of team-mate Lars-Jorgen Salvesen and a flustered Boro defence to slam a low finish home from 12 yards out.
And the day only got worse for Boro with Brittain limping off injured after hurting himself in his attempt to equalise 15 minutes from the end.
Derby County head coach John Eustace told BBC Radio Derby:
“We started slow and the opposition had two or three really good chances and we rode our luck, but as the game went on we grew into it and adapted a couple of things.
“In the second half I felt a lot more comfortable with out shape. We knew we would get a couple of opportunities and I’m delighted to end up winning 1-0.
“Where we lack with a little bit of quality, we make up with determination, grit and heart. I know that group of players will sweat blood for these fans and I think they did that today.
“They really dug in at difficult moments against a really top team.”
Middlesbrough head coach Kim Hellberg told BBC Radio Tees:
“It was unbelievable winning the first four games, having that start. But then getting one point from the next four and not scoring, creating a lot of chances, playing a lot of good football and goalkeepers being the man of the matches almost every game, that hurts.
“Looking at the table, we are back to the same position when we started eight games ago and that hurts also. The result today hurt.
“Look at the bigger picture over those four games and we scored no goals and we created tons of opportunities to score. At the moment we are not good enough at scoring and we have to be honest with that.
“But we cannot just say ‘it’s not going our way’. It’s not, but we have to find a way and get better at those things.
“I go into the locker room and see devastated players. They know it too, they put this on their shoulders. I need to find a way to help them better, that is my job and that’s my aim.”
