The Gunners were 2-1 up but suffered late agony, paving the way for their London rivals to move three points clear at the top of the table
With three results changed by late goals, this weekend's Women's Super League action produced plenty of drama and entertainment once again.
Manchester United brought Arsenal's perfect start to the season to an end with a stoppage-time winner, while West Ham broke the hearts of bottom club Leicester in similar circumstances.
Finally, Liverpool came from two goals down to get a point from Brighton, with the game's final goal coming in the 92nd minute.
So, who had a good week and who had one to forget? GOAL breaks down the chaos below…
GettyWINNER: Chelsea
After watching title rivals Arsenal lose on Saturday, Sunday was the perfect day for Chelsea.
They scored three goals and conceded none in a London derby against Tottenham, putting on a great performance at Stamford Bridge in their first appearance at the stadium this season.
They also welcomed back Emma Hayes for the match, the Blues manager back in the dugout for the first time since undergoing surgery last month, as they went three points clear of the Gunners at the top of the table.
Furthermore, with the champions scoring all three goals in the first half, it meant they were able to make a few early substitutions after the break to rest players ahead of a big midweek fixture, against Real Madrid in the Champions League.
Not a bad weekend at all for Chelsea.
AdvertisementGettyLOSER: Arsenal
Arsenal's 100 per cent record in the league this season came to an end in painful fashion on Saturday evening, with Manchester United running out 3-2 winners at the Emirates thanks to Alessia Russo's stoppage-time header.
After a poor first half, in which they fell behind to an Ella Toone strike, the Gunners took the lead and looked set to see out the win. But United showed incredible character to fight back and take the three points.
It is a setback for Arsenal in their quest for the title, and their first trophy in three years. Fortunately, there is a lot of time left in the season for them to recover.
That will be the interesting thing to watch now, though, as it is the first time this season that this team has failed to win a game of football.
How they respond will be important, particularly given their next fixture is a trip to Juventus in the Champions League to face their old boss, Joe Montemurro.
GettyWINNER: Katie Zelem
Russo grabbed the headlines for her last-gasp winner on Saturday but Katie Zelem was superb in midfield and her set-piece deliveries were crucial to the result.
After helping her team to control large parts of the game, the England international whipped in a superb free-kick in the 85th minute that Millie Turner met brilliantly to thump a header off the underside of the crossbar and into the back of the net.
Once the clock ticked into stoppage time, she then put in another great delivery that Russo connected with to win the game.
Her ability from these situations is deserving of a 'specialist' tag while her overall performance in a huge game will have caught the eye of Sarina Wiegman, the England coach who often picks the midfielder but doesn't give her too many minutes in games.
If she can replicate this level of display on a consistent basis, that will surely change.
GettyLOSER: Brighton
Brighton are often portrayed as a well-drilled, defensively sound team that are difficult to break down. So far this season, we have just not seen that side of them.
On Sunday, it really hurt them, with the Seagulls leading Liverpool 3-1 as early as the 34th minute, only to concede two goals late in the second half – the equaliser in injury time – to drop two points.
Rachel Furness' 92nd-minute goal was the 26th they've conceded in the league this term in just their seventh game. It's a desperately poor record.
The club are still looking for a new coach after the legendary Hope Powell left in the wake of a humiliating 8-0 loss to Tottenham last month and things should improve once that replacement is found.
Powell's successor will look to rectify those issues at the back straight away and if that objective is achieved, Brighton can quickly put any relegation worries behind them, as the reality is, in spite of their long-held reputation, that this is a team with goals in them too.