Southampton await at Wembley on February 26 but Jose Mourinho’s men will need to produce a far better display in the capital after losing this semi-final second leg at relegation-threatened City.
Tom Huddlestone’s penalty was cancelled out by Paul Pogba, only for full debutant Oumar Niasse to give much-changed Hull a shock 2-1 win at the sparsely-filled KCOM Stadium, albeit with United progressing 3-2 on aggregate.
Cup fever had been conspicuous by its absence in the build-up to Thursday’s match, with just 16,831 in attendance due to home fans’ anger at the club’s ownership rather than United’s two-goal advantage.
Marco Silva’s heavily-changed side for Hull’s first home EFL Cup semi-final seemed to justify the decision to stay away, but the match did not go to script as the hosts went ahead through Huddlestone’s penalty.
Mourinho’s frustration at referee Jon Moss’ decision to point to the spot grew as his own side were denied penalties.
Pogba, the world’s most expensive player, prodded home to the audible relief of the travelling masses, who continued to cheer despite United’s’ undefeated run in all competitions coming to a halt.
Niasse turned in at the back post to set up a grandstand finish, but it is Mourinho’s men who are heading to Wembley despite a listless display in East Yorkshire.
There was a distinct testimonial feel around the second leg in the early stages.
Play lacked intensity and excitement as the United supporters made themselves heard, with the chants only pausing when Harry Maguire flashed a shot over and Sam Clucas’ free-kick forced David De Gea into a simple save.
United were going through the motions aside from Marcos Rojo’s deflected half chance and a threatening Zlatan Ibrahimovic cross, whereas a makeshift City were beginning to show signs of life.
As the fans stood to applaud the badly injured Ryan Mason in the 25th minute, Michael Dawson was denied by an excellent Chris Smalling intervention before Niasse was denied by De Gea.
Shaun Maloney missed with a free-kick as Hull continued to threaten underperforming United, who were punished for their lacklustre display in the 35th minute.
Ref Moss controversially pointed to the spot after Rojo was adjudged to have fouled Maguire, with Huddlestone firing home the resulting spot-kick to give Hull hope.
Mourinho was furious as Pogba went down claiming a penalty but to no avail - anger that grew when Smalling went down under pressure from Huddlestone.
United’s frustration made way for relief in the 66th minute. Rashford was denied by a Huddlestone tackle, only for the midfielder to turn into the path of Pogba to direct home through a crowd.
It was a gut punch nearly worsened by Rojo, who found room at a corner to get away a header that hit the crossbar.
Hull’s Wembley dreams were looking bleak but they continued to threaten, with Abel Hernandez being blocked before Niasse hit the crossbar with a fine header.
The loan signing from Everton saw his hard work rewarded with five minutes left.
Niasse directed home a fine David Meyler cross at the far post to set up a nervy ending.
Marshall, Meyler, Dawson, Maguire, Tymon, Huddlestone, Clucas, Bowen (Markovic 59), Maloney (Evandro 64), Diomande (Hernandez 70), Niasse.
de Gea, Darmian, Smalling, Jones, Rojo, Ander Herrera, Carrick, Pogba, Lingard (Rooney 79), Ibrahimovic, Rashford (Fellaini 90).
Jon Moss (W Yorkshire).