Pierre-Emerick Aubameyang's spot kick secured a valuable win for Arsenal against top four rivals Manchester United.

The Gabonese striker bravely grabbed the ball after Fred took out Alexandre Lacazette following his miss vs Tottenham last week.

Granit Xhaka had put the hosts in the lead with a swerving shot that David De Gea bizarrely misjudged.

Ole Gunnar Solskjaer frantically tried to change things in search of a way back into the game.

But after Aubameyang's penalty, there was to be no famous comeback as the Norwegian suffered his first defeat as interim boss. Here are five things we learned.

Player ratings from Arsenal vs Manchester United Show all 22 1 /22 Player ratings from Arsenal vs Manchester United Player ratings from Arsenal vs Manchester United Bernd Leno - 8 Arsenal's German goalkeeper Bernd Leno (L) smoothers a shot from Manchester United's Belgian forward Romelu Lukaku (C) during the English Premier League football match between Arsenal and Manchester United at the Emirates Stadium in London on March 10, 2019. (Photo by Ben STANSALL / AFP) / RESTRICTED TO EDITORIAL USE. No use with unauthorized audio, video, data, fixture lists, club/league logos or 'live' services. Online in-match use limited to 120 images. An additional 40 images may be used in extra time. No video emulation. Social media in-match use limited to 120 images. An additional 40 images may be used in extra time. No use in betting publications, games or single club/league/player publications. / BEN STANSALL/AFP/Getty Images BEN STANSALL AFP/Getty Images Player ratings from Arsenal vs Manchester United Sokratis Papastathopoulos - 6 Arsenal's Greek defender Sokratis Papastathopoulos (L) helps up Manchester United's French midfielder Paul Pogba (R) during the English Premier League football match between Arsenal and Manchester United at the Emirates Stadium in London on March 10, 2019. (Photo by Ben STANSALL / AFP) / RESTRICTED TO EDITORIAL USE. No use with unauthorized audio, video, data, fixture lists, club/league logos or 'live' services. Online in-match use limited to 120 images. An additional 40 images may be used in extra time. No video emulation. Social media in-match use limited to 120 images. An additional 40 images may be used in extra time. No use in betting publications, games or single club/league/player publications. / BEN STANSALL/AFP/Getty Images BEN STANSALL AFP/Getty Images Player ratings from Arsenal vs Manchester United Laurent Koscielny - 7 Soccer Football - Premier League - Arsenal v Manchester United - Emirates Stadium, London, Britain - March 10, 2019 Arsenal's Laurent Koscielny in action REUTERS/Eddie Keogh EDITORIAL USE ONLY. No use with unauthorized audio, video, data, fixture lists, club/league logos or "live" services. Online in-match use limited to 75 images, no video emulation. No use in betting, games or single club/league/player publications. Please contact your account representative for further details. EDDIE KEOGH REUTERS Player ratings from Arsenal vs Manchester United Nacho Monreal - 6 LONDON, ENGLAND - MARCH 10: Romelu Lukaku of Manchester United in action with Nacho Monreal during the Premier League match between Arsenal FC and Manchester United at Emirates Stadium on March 10, 2019 in London, United Kingdom. (Photo by John Peters/Man Utd via Getty Images) John Peters Man Utd via Getty Images Player ratings from Arsenal vs Manchester United Ainsley Maitland-Niles - 6 Manchester United's Luke Shaw, left, and Arsenal's Ainsley Maitland-Niles challenge for the ball during the English Premier League soccer match between Arsenal and Manchester United at the Emirates Stadium in London, Sunday, March 10, 2019. (AP Photo/Tim Ireland) Tim Ireland AP Player ratings from Arsenal vs Manchester United Sead Kolasinac - 8 Arsenal's Lead Kolasinac, left, and Manchester United's Fred challenge for the ball during the English Premier League soccer match between Arsenal and Manchester United at the Emirates Stadium in London, Sunday, March 10, 2019. (AP Photo/Tim Ireland) Tim Ireland AP Player ratings from Arsenal vs Manchester United Granit Xhaka - 8 LONDON, ENGLAND - MARCH 10: Granit Xhaka celebrates scoring a goal for Arsenal during the Premier League match between Arsenal FC and Manchester United at Emirates Stadium on March 10, 2019 in London, United Kingdom. (Photo by David Price/Arsenal FC via Getty Images) David Price Arsenal FC via Getty Images Player ratings from Arsenal vs Manchester United Aaron Ramsey - 7 Arsenal's Swiss midfielder Granit Xhaka (R) celebrates scoring the opening goal with Arsenal's Welsh midfielder Aaron Ramsey (L) during the English Premier League football match between Arsenal and Manchester United at the Emirates Stadium in London on March 10, 2019. (Photo by Ian KINGTON / IKIMAGES / AFP) / RESTRICTED TO EDITORIAL USE. No use with unauthorized audio, video, data, fixture lists, club/league logos or 'live' services. Online in-match use limited to 45 images, no video emulation. No use in betting, games or single club/league/player publications.IAN KINGTON/AFP/Getty Images IAN KINGTON AFP/Getty Images Player ratings from Arsenal vs Manchester United Mesut Ozil - 6 Soccer Football - Premier League - Arsenal v Manchester United - Emirates Stadium, London, Britain - March 10, 2019 Arsenal's Mesut Ozil gestures Action Images via Reuters/John Sibley EDITORIAL USE ONLY. No use with unauthorized audio, video, data, fixture lists, club/league logos or "live" services. Online in-match use limited to 75 images, no video emulation. No use in betting, games or single club/league/player publications. Please contact your account representative for further details. JOHN SIBLEY Action Images via Reuters Player ratings from Arsenal vs Manchester United Pierre-Emerick Aubameyang - 7 Soccer Football - Premier League - Arsenal v Manchester United - Emirates Stadium, London, Britain - March 10, 2019 Arsenal's Pierre-Emerick Aubameyang looks on REUTERS/Eddie Keogh EDITORIAL USE ONLY. No use with unauthorized audio, video, data, fixture lists, club/league logos or "live" services. Online in-match use limited to 75 images, no video emulation. No use in betting, games or single club/league/player publications. Please contact your account representative for further details. EDDIE KEOGH REUTERS Player ratings from Arsenal vs Manchester United Alexandre Lacazette - 8 Arsenal's Swiss midfielder Granit Xhaka (R) celebrates scoring the opening goal with Arsenal's French striker Alexandre Lacazette (L) during the English Premier League football match between Arsenal and Manchester United at the Emirates Stadium in London on March 10, 2019. (Photo by Ben STANSALL / AFP) / RESTRICTED TO EDITORIAL USE. No use with unauthorized audio, video, data, fixture lists, club/league logos or 'live' services. Online in-match use limited to 120 images. An additional 40 images may be used in extra time. No video emulation. Social media in-match use limited to 120 images. An additional 40 images may be used in extra time. No use in betting publications, games or single club/league/player publications. / BEN STANSALL/AFP/Getty Images BEN STANSALL AFP/Getty Images Player ratings from Arsenal vs Manchester United David De Gea - 4 LONDON, ENGLAND - MARCH 10: David De Gea of Manchester United looks dejected during the Premier League match between Arsenal FC and Manchester United at Emirates Stadium on March 10, 2019 in London, United Kingdom. (Photo by Catherine Ivill/Getty Images) Catherine Ivill Getty Player ratings from Arsenal vs Manchester United Ashley Young - 6 Arsenal's Mesut Ozil controls the ball ahead of Manchester United's Ashley Young during the English Premier League soccer match between Arsenal and Manchester United at the Emirates Stadium in London, Sunday, March 10, 2019. (AP Photo/Tim Ireland) Tim Ireland AP Player ratings from Arsenal vs Manchester United Chris Smalling - 5 LONDON, ENGLAND - MARCH 10: Chris Smalling of Manchester United in action with Sead Kolasinac during the Premier League match between Arsenal FC and Manchester United at Emirates Stadium on March 10, 2019 in London, United Kingdom. (Photo by John Peters/Man Utd via Getty Images) John Peters Man Utd via Getty Images Player ratings from Arsenal vs Manchester United Victor Lindelof - 5 Manchester United's Victor Lindelof, left, and Arsenal's Pierre-Emerick Aubameyang challenge for the ball during the English Premier League soccer match between Arsenal and Manchester United at the Emirates Stadium in London, Sunday, March 10, 2019. (AP Photo/Tim Ireland) Tim Ireland AP Player ratings from Arsenal vs Manchester United Luke Shaw - 6 LONDON, ENGLAND - MARCH 10: Luke Shaw of Manchester United runs with the ball during the Premier League match between Arsenal FC and Manchester United at Emirates Stadium on March 10, 2019 in London, United Kingdom. (Photo by Julian Finney/Getty Images) Julian Finney Getty Images Player ratings from Arsenal vs Manchester United Nemanja Matic - 5 LONDON, ENGLAND - MARCH 10: Mesut Ozil of Arsenal is challenged by Nemanja Matic of Manchester United during the Premier League match between Arsenal FC and Manchester United at Emirates Stadium on March 10, 2019 in London, United Kingdom. (Photo by Julian Finney/Getty Images) Julian Finney Getty Images Player ratings from Arsenal vs Manchester United Diogo Dalot - 5 Soccer Football - Premier League - Arsenal v Manchester United - Emirates Stadium, London, Britain - March 10, 2019 Arsenal's Laurent Koscielny in action with Manchester United's Diogo Dalot REUTERS/Eddie Keogh EDITORIAL USE ONLY. No use with unauthorized audio, video, data, fixture lists, club/league logos or "live" services. Online in-match use limited to 75 images, no video emulation. No use in betting, games or single club/league/player publications. Please contact your account representative for further details. EDDIE KEOGH REUTERS Player ratings from Arsenal vs Manchester United Fred - 7 Arsenal's Lead Kolasinac, left, and Manchester United's Fred challenge for the ball during the English Premier League soccer match between Arsenal and Manchester United at the Emirates Stadium in London, Sunday, March 10, 2019. (AP Photo/Tim Ireland) Tim Ireland AP Player ratings from Arsenal vs Manchester United Paul Pogba - 5 Manchester United's French midfielder Paul Pogba (L) plays the ball in front of Arsenal's English midfielder Ainsley Maitland-Niles (R) during the English Premier League football match between Arsenal and Manchester United at the Emirates Stadium in London on March 10, 2019. (Photo by Ian KINGTON / IKIMAGES / AFP) / RESTRICTED TO EDITORIAL USE. No use with unauthorized audio, video, data, fixture lists, club/league logos or 'live' services. Online in-match use limited to 45 images, no video emulation. No use in betting, games or single club/league/player publications.IAN KINGTON/AFP/Getty Images IAN KINGTON AFP/Getty Images Player ratings from Arsenal vs Manchester United Romelu Lukaku - 6 LONDON, ENGLAND - MARCH 10: Bernd Leno of Arsenal reaches for the ball as Romelu Lukaku of Manchester United shoots during the Premier League match between Arsenal FC and Manchester United at Emirates Stadium on March 10, 2019 in London, United Kingdom. (Photo by Julian Finney/Getty Images) Julian Finney Getty Images Player ratings from Arsenal vs Manchester United Marcus Rashford - 6 LONDON, ENGLAND - MARCH 10: Marcus Rashford of Manchester United stretches for the ball during the Premier League match between Arsenal FC and Manchester United at Emirates Stadium on March 10, 2019 in London, United Kingdom. (Photo by Julian Finney/Getty Images) Julian Finney Getty Images

1. Arsenal show true potential

It was only six weeks ago that Arsenal were embarrassed here by Manchester United in the FA Cup, picked apart on the break losing 3-1. That day it felt as if Arsenal had no real idea what they were doing, as the blindly played straight into United’s hands. Today was very different. Arsenal had a far clearer identity, far better tactics, and looked better prepared for the contest.

They did not throw too many men forward in attack, and the back line kept a far better handle on things than you might have feared. Their 3-4-1-2 system allowed them to dominate down the flanks and control midfield from the start, forcing United into a change.

It has been one step forward one step back for Arsenal all season but this certainly felt like progress, one of their best wins of the season, containing promise for next season too. The challenge now is to maintain it.

Aubameyang scores from the spot (Getty)

2. Aubameyang and Lacazette thrive together

There is a lot to be said for playing your best players. That might sound trite but it has not always been the case at Arsenal this season. Pierre Emerick Aubameyang and Alexandre Lacazette are obviously their best two players but Unai Emery has not always wanted to play the two together.

He did it consistently in January but after a 3-1 defeat at the Etihad Stadium he had a rethink, prompting a seven-game run in which it was always one or the other but never both. Here he returned to the strike pairing and was emphatically rewarded. Lacazette and Aubameyang’s movement was electric, never letting United relax, pulling their defence apart.

And Lacazette won the penalty that Aubameyang converted. Arsenal fans will hope for more of the same from one of the best old-fashioned strike pairings in the country.

Xhaka and Lacazette celebrate (AFP/Getty Images)

3. Leno shows value

Fresh from his miraculous double save against Tottenham at Wembley last Saturday, Bernd Leno had another one of those games in goal when he looks like the best decision Arsenal have made in recent years. He looks more assured every week and shone again here under some serious examination.

He has uncanny reflexes and is quick off his line, as he showed here more than once darting out to stop Romelu Lukaku and Marcus Rashford. He even at one point ran 30 yards out from his goal to pass the ball, looking just as comfortable as Ederson does when he plays like that.

The fact that you could never picture Petr Cech doing that shows what an important change it was to replace him with Leno, helping Arsenal to play the way they want to.

4. Solskjaer shows proactive approach

There is more to Ole Gunnar Solskjaer’s management than just nostalgia and motivation. On Wednesday night in Paris Solskjaer hauled off Eric Bailly in the first half because United were struggling so much, a change that helped to turn the game their way.

Here he showed the same proactivity, making a tactical change long before half-time. United started with a 4-4-2 but it did not work, they were picked around in midfield and outnumbered down the flanks.

So Solskjaer switched to a 5-3-2 that gave them more stability in the middle and more cover out wide. It might not have been the obvious solution given the players he had, it meant Ashley Young playing as a makeshift centre-back. Ultimately United still lost, but this decision did at least give them the opportunity to get back into the game.

Solskjaer’s tweaks failed to turnaround the match (AFP/Getty)

5. Ozil fails to convince

It says a lot about Mesut Ozil’s declining status at Arsenal that it was a surprise to see him here starting such a serious game. Because recently Unai Emery has only used him in low-key fixtures to unpick defensive teams.

In the last four months he has only started against Wolves, Qarabag, Burnley, Brighton, Cardiff City, BATE Borisov, Bournemouth and Rennes. And yet here he was up against Manchester United, given a platform to play in one of the biggest games of all.