United’s head coach will try hard to forget his first experience of a Yorkshire derby but no fewer than nine bosses in the Championship can share stories of upsets after an unforgiving first round.
The cost to Rosler was not so much the humiliation as the loss of Lewis Cook for three league games.
The midfielder walked the slow walk a few moments after Doncaster, Paul Dickov’s feisty League One side, replied to his effort with a penalty from Andy Williams and the advantage of an extra player gave Rovers most of the remaining minutes of normal time.
They flogged United’s defence without breaking a belligerent wall in front of the excellent Ross Turnbull.
An away crowd of more than 3,000 – close to half the attendance – fought the tide along with Rosler’s players, applauded by the German as Leeds tried to hold out, and United dragged the tie into extra-time with guts and 10 men.
Gradually they regained their composure and tempted a tiring Rovers team to settle for penalties.
A shoot-out eventually stood between the clubs and the second round but having hung in gamely, Sam Byram and Chris Wood skied their efforts over the crossbar as Doncaster buried all four of their strikes.
In pouring rain, Leeds looked shattered. The League Cup claimed another scalp.
Rosler was less than thrilled by Sky Sports’ idea of a Thursday night game and an additional half hour of football increased the weight of an already heavy schedule.
He planned for games to come by making five changes to his line-up and choosing a team in which Scott Wootton played as an experimental holding midfielder.
That decision was risky and it backfired before half-time as Wootton conceded a penalty and Cook incurred his red card, leaving Alex Mowatt as the only recognised midfielder in United’s side.
Several big hitters dropped to the bench, captain Sol Bamba included, and his absence left Giuseppe Bellusci and Liam Cooper to pair up in the centre of defence.
Wootton, who cameoed in midfield towards the end of Saturday’s draw with Burnley, was thrown in there from the outset by Rosler and his 30th-minute foul on Cedric Evina turned a game that was going to plan.
Until then, Leeds’ performance kept the ball a long way from Turnbull’s goal.
The former Chelsea goalkeeper – the pick of Rosler’s players last night – deputised for Marco Silvestri and was bothered only once before Rovers’ equaliser.
After that, however, Doncaster came at him, enthused by Cook’s dismissal and their own recovery from a bad start.
The early stages of the game went as Rosler intended and Leeds prodded Doncaster repeatedly, testing the right side of their defence. In the 15th minute they found a weak spot which Mirco Antenucci exploited brilliantly.
The striker took a pass from Mowatt and tore away from Rob Jones, leaving the tall centre-back for dead and forcing keeper Thorsten Stuckmann to push a low shot back out into his box. Cook arrived with perfect timing and cushioned a bouncing ball into Stuckmann’s net.
The goal was 18-year-old’s first for the club and should have drawn the sting from Rovers but Leeds almost contrived to gift Doncaster parity seven minutes later.
Williams forced a chip through to an unmarked James Coppinger who sized up Turnbull and lifted a lob over his head. Bellusci chased the bouncing ball and hooked it off the line at full stretch.
Doncaster took encouragement from that but the pressure was still more keen at the other end of the pitch.
Souleymane Doukara created one chance by dribbling into the box and whipping a cross in front of Mowatt, who clattered into Stuckmann unintentionally, and the forward laid on a second by teeing the ball up nicely for Stuart Dallas.
Stuckmann looked exposed momentarily but Andy Butler’s sliding tackle turned Dallas’ shot out of play.
With the game in hand and half an hour gone, a loose tackle from Wootton contrived to change the balance of the evening.
His attempt to nick possession from Evina took the winger’s legs from under him and referee Keith Hill did not think long before awarding a penalty.
Williams’ finish was unconvincing but firm enough to squirm under Turnbull’s body.
Worse was to come and with 36 minutes gone Cook brought up another career first, shown a straight red card for a two-footed tackle on Doncaster left-back Taylor-Sinclair.
Committed wide on the touchline, Cook knew the severity of his foul as soon as he connected and made no protest when Hill sent him from the field. Replays explained Cook’s obvious remorse.
Rosler sat tight in the remainder of the half and held off from making substitutions at half-time.
With just over 20 minutes to go, Rosler turned to Chris Wood and Luke Murphy in the hope of stemming Doncaster’s dominance, pinching a winner and avoiding extra-time.
Sam Byram appeared soon afterwards, a substitute who Rosler would have intended not to use with Reading on Sunday looming.
Wood made a strong appeal for a penalty when Luke McCullough tussled with him beneath a high cross but Hill looked away and Rovers fought desperately to tease a mistake out of Rosler’s besieged defence.
Williams’ nervous header bounced wide and an array of shots from Coppinger sailed wide of Turnbull’s net.
Into extra-time, where Antenucci was deeply unlucky to see a deflected shot hit the inside of a post and rebound into Stuckmann’s arms in the 105th minute, at a point where Rovers were backpedalling and losing their grip, and penalties felt inevitable from there on.
Antenucci and Murphy traded successful spot kicks with Nathan Tyson and Williams before Byram’s wayward finish and a rash hit from Wood gave Harry Forrester and Richie Wellens the chance to finish Leeds off.
As experienced a professional as either side had to call upon, Wellens struck the killer blow.