Arsenal came from behind to secure a fully deserved north London derby win and inflict damage on Tottenham’s hopes of a place in the Premier League’s top four.
The Gunners were vastly superior until a Spurs rally in the closing stages but fell behind to a piece of genius from Erik Lamela – on for the injured Son Heung-Min – when he curved a magnificent rabona finish beyond Arsenal keeper Bernd Leno in the 33rd minute.
Arsenal, who had seen Emile Smith Rowe’s long-range shot smack against the bar, then suffered more ill-luck when Cedric Soares hit the post, but were level on the stroke of half-time when Martin Odegaard’s effort was deflected out of the reach of Spurs keeper Hugo Lloris.
Mikel Arteta’s side continued to dominate a largely dreadful Spurs and took the lead from the penalty spot after 64 minutes when Alexandre Lacazette missed his kick but was fouled by Davinson Sanchez.
Lacazette recovered to send Lloris the wrong way for his 12th goal of the season.
Spurs’ day got worse when Lamela was sent off for a second yellow card, shown by referee Michael Oliver for a hand-off into the face of Kieran Tierney with 14 minutes left.
But they almost snatched a point in the closing moments when Harry Kane’s free-kick bounced off the post, with Arsenal defender Gabriel heading Sanchez’s goal-bound shot off the line from the rebound.
Arsenal, who dropped captain Pierre-Emerick Aubameyang for the game for disciplinary reasons, stay in 10th place but Spurs are now six points adrift of Chelsea in fourth, although with a game in hand.
Arteta showed discipline is paramount – and no one is above his law – by dropping skipper and main striker Aubameyang to the bench for what Arsenal described as “a breach of pre-match protocol”.
It was a big game to have to make this choice but Arteta demonstrated who was boss and was rewarded not just with a vital derby victory but also a fine performance, watched from the sidelines by the solemn figure of the chastened Aubameyang.
Arsenal, even without their captain and most prolific marksman, were by far the more dangerous side, taking control from the start and only showing signs of nerves when Spurs mounted a belated late surge which almost brought them a point they did not merit.
Smith Rowe was outstanding for Arsenal while Odegaard got his first Premier League goal and Lacazette won and scored the decisive penalty.
Arsenal remain a team in transition but they played some fine football here and this will surely boost confidence and self-belief as they try to navigate a route into Europe next season, the three points tasting even sweeter as they were taken at the expense of their arch-rivals.
Aubameyang will no doubt return in due course, punishment served, but Arteta showed the courage of his convictions and this turned out to be a highly satisfactory day for Arsenal’s manager.
This was a miserable day all round for Mourinho and Spurs as they lost Son early on to a hamstring injury, goalscorer Lamela was sent off and they wasted the opportunity to make up ground on the top four with a performance that was, for the most part, abject and negative.
Lamela’s moment of genius, his rabona finish, a rare shaft of light for Spurs, ultimately counted for nothing as the visitors left it far too late to raise the tempo.
Indeed, it was only after Lamela was sent off and they were at a numerical disadvantage that Spurs applied any serious pressure, although that almost brought a point as Kane hit the post and Sanchez’s shot was cleared off the line by Gabriel.
Why Spurs waited until their backs were against the wall and their cause desperate to show any urgency is a mystery. They must see this as a missed opportunity.
Gareth Bale’s long cross in the build-up to Lamela’s goal was his only serious contribution before he was substituted in the second half and Spurs failed to get any meaningful service to Kane.
Spurs have now lost six and drawn four of their past 10 Premier League games at Arsenal and have now been beaten in nine league games this season, the joint most Mourinho has lost in a campaign in his managerial career.
This was a day that did not contain much good news for either Mourinho or Spurs.