Mata scored the only goal as Manchester United edged past their neighbours to claim a place in the League Cup quarter-finals.
And it means Guardiola has gone six games without a win for the first time in his stellar managerial career.
But it always felt this game was more important for Jose Mourinho and United than Guardiola and City.
That was reflected in their team selections and it was the way the night panned out.
Having lost the first derby at home last month and coming into the game off the back of their Stamford Bridge embarrassment, United could ill afford another setback in a big game.
City’s shadow squad certainly put up a tremendous fight and had the better of the first half. But United were transformed after the break and Mata scored from 12 yards after being set up by Zlatan Ibrahimovic. It means they end their critical four games in a 10-day spell on an upbeat note with home wins over City and Fenerbahce and a draw at Anfield diluting somewhat the shock waves of the defeat at Chelsea.
Manchester United and Manchester City combined XI
Wed, October 26, 2016Express Sport has picked an XI made from the cream of both Manchester sides ahead of tonight's EFL Cup clash at Old Trafford (8pm)
Express Sport runs through our best possible combined XI from players that could feature in tonight’s Manchester derby, although it is more than likely plenty of young guns will actually get the nod in the EFL Cup clash
Mourinho has always treated the League Cup seriously, winning it three times in his two spells in charge with Chelsea.
He recalled Michael Carrick in place Marouane Fellaini, and made United’s oldest player his captain, while Mata, Marcos Rojo and Luke Shaw came in for Eric Bailly, Chris Smalling – who are both injured – and Jesse Lingard. Guardiola was true to his word and fielded a much-changed team. Only Vincent Kompany and Leroy Sane remained from the side that drew 1-1 with Southampton on Sunday.
Youngsters Aleix Garcia and Pablo Maffeo were included in the City line-up but City made the better start, with Garcia looking very assured on the big stage in midfield and right-back Maffeo keeping a tight rein on Marcus Rashford.
There were only 90 seconds on the clock when the visitors served notice of intent. Garcia sent Jesus Navas on a run past Shaw down the right and his superb cross was bundled over the crossbar by a stumbling Iheanacho.
It took 22 minutes before United won a corner, when Ibrahimovic’s free-kick deflected off the wall, but Daley Blind’s delivery was poor and United started to look frustrated at their inability to find any rhythm, with passes frequently misplaced.
They finally threatened in the 35th minute, Ibrahimovic’s shot deflecting off Nicolas Otamendi and over the bar. That gave them some encouragement. Moments later Ibrahimovic sent Rashford away but his route to goal was blocked by a crowd of City players.
Paul Pogba had been pretty anonymous again, although his dangerous cross was clawed away from Ibrahimovic by Willy Cabellero. But again United ruined their momentum by giving the ball away. When Blind’s pass was cut out, he was rescued by Rojo’s sliding block on Iheanacho. Moments later, after Ibrahimovic had given the ball away again, De Gea had to come racing of his line to deny Iheanacho.
No doubt fired up by a few choice words from Mourinho, United made a much more positive start to the second half. They were also boosted by the departure of City skipper Kompany with another injury scare.
Ibrahimovic showed a big improvement. He slipped the ball through Otamendi’s legs before setting up the overlapping Pogba for shot Caballero tipped onto the post.
Rashford had the crowd on their feet when eluding two hefty challenges as he burst down the left, and a flurry of shots were to warn of what was to come.
Ibrahimovic used all his wily experience as United scored the winner after 54 minutes. He bundled over Otamendi in an aerial challenge before taking the ball into the penalty area. Instead of shooting he played a square pass and when Herrera collided with Fernando – perhaps illegally – as the City midfielder attempted to get to the ball, it ran on to Mata, who crashed home a low shot from 12 yards.
Man United (4-2-3-1): De Gea; Valencia, Rojo, Blind, Shaw; Herrera, Carrick; Mata (Schneiderlin 73), Pogba, Rashford (Lingard 81); Ibrahimovic. Booked: Valencia, Pogba. Goal: Mata 54. NEXT UP: Burnley (h), Sat PL.
Man City (4-1-4-1): Cabellero; Maffeo, Kompany (Kolarov 46), Otamendi, Clichy; Fernando; Navas, Garcia, Sane (Sterling 63), Nolito (Aguero 71); Iheanacho. Booked: Iheanacho. NEXT UP: West Brom (a), Sat PL.
Referee: M Dean (Wirral).