Manchester United suffered another shock League Cup exit as they were beaten 3-1 on penalties by Middlesbrough following a 0-0 draw on Wednesday.
Louis van Gaal's much-changed side controlled the majority of the fourth-round tie, but it was Middlesbrough who created the best chances over 90 minutes, with Stewart Downing coming close and the recalled Daley Blind spared a remarkable own goal by the offside flag.
Jesse Lingard hit the woodwork for the home side and Sergio Romero twice saved superbly to deny Boro a dramatic late winner in normal time, after an earlier howler had come close to gifting them the lead.
Anthony Martial came agonisingly close with an extra-time header and Marouane Fellaini failed to convert with the goal at his mercy, but Aitor Karanka's superbly drilled defence held strong to force a penalty shootout under the Old Trafford lights.
David Nugent missed for the visitors, but Wayne Rooney, Michael Carrick and Ashley Young also all failed to convert to hand Boro a quarter-final spot and condemn United to another exit to lower-league opposition following last season's 4-0 humbling against MK Dons in the same competition.
It was the visitors, fourth in the Championship, who carved out the first chance of the match, with Emilio Nsue's scuffed attempt at an overhead kick falling to George Friend just a couple of yards out, but he could only shoot straight at Romero.
Fellaini dragged a left-footed shot wide of the far post after turning well on the edge of the box, and the Belgium international teed up James Wilson for a tame effort hit straight at Tomas Mejias a few moments later.
Fellaini saw another effort blocked at the near post before Downing had Romero at full stretch with a fierce strike from 25 yards as the half finished evenly.
With Rooney brought on at the break, United stepped up the pace early in the second half. High pressing gave Memphis Depay the chance to shoot from 20 yards, with the ball spinning out of Mejias' grasp and almost crossing the line.
Boro thought they had snatched the lead just before the hour mark when Blind bizarrely fired the ball straight into his own net after Kike had hit the post, but the offside flag was raised against the striker's first effort.
Lingard's fine solo run brought another save from Mejias, but United had another lucky escape when Romero completely miscontrolled a backpass that bounced inches wide of the far post.
Romero atoned with a strong near-post stop to deny Ben Gibson as United, with Martial on for the disappointing Depay, began to set up camp in the Boro half in search of a late winner.
Lingard was denied by the post as he smashed Young's cross goalwards, but Romero saved the home side in the dying minutes, reacting well to deny Grant Leadbitter on the break before diving to his right to keep out Downing's low drive.
The game remained wide open as extra-time began. Leadbitter shot straight against Chris Smalling when unmarked in the area before Fellaini just failed to connect with Andreas Pereira's clipped cross to the far post.
Pereira himself fired inches wide from 20 yards in the closing minutes before Martial's diving header somehow spun just past the post, and Fellaini headed over when unmarked just yards from goal, meaning penalties were required.
Rooney's effort was tipped past the post and Nugent blazed over before Michael Carrick cleared the crossbar to hand Boro the advantage.
Gibson fired high into the net and Mejias saved Young's weak effort to his right to send the visiting fans into raptures.
