Kevin de Bruyne and Kelechi Iheanacho scored the goals as Manchester City survived a debut boob by Claudio Bravo to deservedly beat Manchester United 2-1.
City dominated for large spells of the derby at Old Trafford and but for Bravo dropping a routine free-kick on the stroke of half-time, which allowed Zlatan Ibrahimovic to half-volley home, they would have cruised to three points.
The impressive Kevin de Bruyne (15) slotted the visitors ahead after Aleksandar Kolarov’s long ball foward was flicked on by Iheanacho and de Bruyne hit the post before Iheanacho tapped in the second on 36 minutes.
Ibrahimovic brilliantly reduced the arrears with a half-volley after Bravo had dropped a deep free-kick at the feet of the Swede.
The eyes of the sporting world were focused on Old Trafford as two of the world’s most high-profile managers renewed hostilities on Saturday lunchtime, having endured a frosty, tempestuous battle for LaLiga glory for several years.
Now they share a city and the desire for Premier League glory, with Guardiola striking the first blow as a fine first-half display saw City run out 2-1 victors as United’s 100 per cent start to life under Mourinho came to a halt.
De Bruyne was the catalyst for the visitors, coolly opening the scoring after nipping past Daley Blind before firing a shot that hit the post and rebounded kindly for Kelechi Iheanacho to deservedly extend City’s lead.
Mourinho’s side, by contrast, were struggling until debutant goalkeeper Bravo’s composure disappeared with his clean sheet, flapping at a Wayne Rooney free-kick as Ibrahimovic fired home with aplomb before the break.
Joe Hart’s replacement looked flustered and was fortunate not to give away a penalty or collect a card soon after the restart, turning into danger and lunging at Rooney in the box.
A United equaliser was ruled out as exciting substitute Marcus Rashford’s strike deflected home off the offside Ibrahimovic, with De Bruyne hitting the post at the other end as City held on for an important victory on enemy turf.
Mourinho and Guardiola shook hands as the final whistle signalled three points for the visitors on an afternoon when the players’ battle rather than ructions between the managers dominated the conversation.
City held on as United paid for an undercooked first half, with De Bruyne turning a fine start into a 15th-minute opener.
Bravo’s short pass to Kolarov was sent long and Iheanacho flicked onwards. It was a ball Blind should have cleared, only to see De Bruyne dart past him and though on goal to tuck home past David de Gea.
The opener led tensions to ratchet up as Guardiola and Rooney came together on the touchline, with United’s frustration contrasting markedly with City’s confidence.
Bacary Sagna’s audacious volleyed attempt epitomised that and the visiting support were celebrating their second of afternoon in the 36th minute.
De Bruyne was again key to the goal, turning superbly and hitting a shot that came back off the post for Iheanacho to tap home.
Played onside by Blind, it appeared a killer blow but United reduced the deficit three minutes before the break thanks to Bravo’s gaffe.
Rooney’s floated free-kick looked too high and slow to trouble Hart’s replacement, yet the Chilean flapped at the ball as John Stones looked to clear and Ibrahimovic fired home superbly.
Bravo prevented the Swede from grabbing a quick-fire second when meeting a Rooney cross from an acute angle, but the goalkeeper was clearly flustered.
Misreading when darting out to win the ball, Jesse Lingard instead won possession but Ibrahimovic wasted the chance to level.
Mourinho shuffled the pack at the break as the largely anonymous Lingard and Henrikh Mkhitaryan were replaced by Ander Herrera and Rashford.
The latter, buoyed by a midweek hat-trick for England Under-21s, was quickly involved, clipping in for Ibrahimovic to volley over before having an effort blocked.
Ibrahimovic and Marouane Fellaini were booked in quick succession as United upped the ante, with Fernando replacing Iheanacho in a bid to stem the tide.
It worked largely but Bravo was still looking rattled and was guilty of overplaying at the back. Turning away from Herrera but into danger, the 33-year-old had to lunge to prevent gifting possession to Rooney – but referee Mark Clattenburg ignored calls for punishment.
The home fans were further frustrated when Antonio Valencia’s cross struck Nicolas Otamendi but no spot-kick was forthcoming.
The tension lifted temporarily as Rashford burst down the flank and found the net, only for offside to be rightly called after the ball took a deflection off Ibrahimovic.
De Gea was having to be alert to stop City putting the game out of sight, but there was little he could do but breathe a sigh of relief as De Bruyne struck the post from an acute angle.
The chances were flowing as United pushed for a leveller and left gaps at the back, with Rooney thwarted and Ibrahimovic unable to get a shot on target before Stones hacked clear late on.