Butron Albion stunned Championship side Middlesbrough 1-0 to advance to the Carabao Cup semi-finals.
Tony Pulis made six changes from the side that lost to Queens Park Rangers and they looked like a disjointed side.
Middlesbrough were made to pay for an untidy start to the second half as Burton’s Jake Hesketh broke the deadlock after 48 minutes.
After Jamie Allen’s strike had hit the post, Hesketh recovered from a slip to fire the ball into the bottom corner from the edge of the area.
Aden Flint came agonisingly close to finding an equaliser for Boro in the 83rd minute when he got on the end of a cross in Burton’s box but his effort went wide.
But League One Burton held on to book their place in the semi-finals.
The visitors tested keeper Darren Randolph for the first time, although not to any great extent, when defender Ben Turner got his head to Scott Fraser’s back-post cross, but opposite number Collins needed to be alert to to claw away Downing’s 28th-minute free-kick.
Stephen Quinn lifted a snapshot over the bar 12 minutes before the break as the Brewers responded, but both Collins and Jake Buxton had to block efforts from Hugill in quick succession after he had been played in over the top by Muhamed Besic.
But Harness might have handed Burton the lead in stoppage time after Hesketh had stepped over Lucas Akins’ cross, only for the winger to sidefoot wastefully over.
Tony Pulis’ men made an untidy start tot he second half, and were made to pay within three minutes when, after Fry had given the ball away, Fraser played in Jamie Allen and although his shot came back off the far post, Hesketh rifled the rebound past the diving Randolph.
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Boro were in disarray and might have fallen further behind within four minutes when Harness show a shot deflected over the bar and with a fightback failing to materialise, the manager made his move when he sent on Marcus Tavernier and Britt Assombalonga for Besic and Hugill with 27 minutes remaining.
But the home side were simply unable to summon up the quality they needed to rescue themselves with Flint somehow heading Tavernier’s cross wide at the death on a famous night for the men from the Pirelli Stadium.