A spot in the top four was lost due to this game.
In the middle of April, the Saints were without a win in five and had just been humiliated by the Blues. This was the perfect opponent to get back on track for the top four.
Mikel Arteta was forced to take a weakened squad to St Mary's because of injuries to several players. A lack of quality and sharpness let them down.
Both the match and the top-four race have been affected by the loss of the Gunners. In the last six games of the season, the Saints only picked up one point.
In a completely different context, Arsenal will return to Saints on Super Sunday. They are four points clear of Manchester City at the top of the table, with their best ever start to a season.
Can Arteta's team maintain their excellent start and become the main challengers to City? The answer to the question of squad depth was no.
"Manchester City can lose a few players and play exactly the same way and can afford to rotate," said Sky Sports pundit.
All of a sudden they become a different team if Gabriel Jesus, Oleksandr, and Thomas Partey are lost.
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This lack of depth derailed the end of last season. Arteta had to change his back-up options because of the loss of Partey.
Arteta could not make a decision on who to replace Tierney with. Partey was dropped by the manager for Elneny after poor performances.
In the first three games after Partey and Tierney's injuries, they lost three of them.
Arteta didn't have enough in reserve to support his regulars. Do the same depth issues remain as they try to win the title after making very few changes to his regular line-up?
After no European football last season, it was important for the club to strengthen their squad with their spot in theEuropa League confirmed.
There are two vacancies where the north Londoners are still short.
There were reports of late interest in Wolves winger Pedro Neto, but a transfer for Douglas Luiz failed to come to fruition. Failure to get the two targets means central midfield, more specifically Partey's role, and right wing are areas of concern for the club.
Partey is not reliable enough to be considered available every week and there is reason to plan around that.
Lokonga has already deputized for Partey's injuries this season, but Arteta's team has more control when the Ghanaian starts, scoring twice as many goals with him in the team and allowing more than they score when he's absent.
Elneny and Oleksandr were both injured at the start of the season.
Too much was asked of the right wing player. Only one other player in the top flight last season was able to challenge him for a starting spot, leaving him as the only one to play in all 38 games.
With zero open play goals and two assists in the last 10 league games of the season, the goal scoring exploits that Saka has now - five goals and four assists in his last eight starts - faded away.
If Arteta wants to keep Jesus in a centre forward role instead of the wide position he used to find himself at Manchester City, then the only real options are new signings Marquinhos and Joao Cancelo.
Marquinhos, 19, who has enjoyed some promising Europa League starts in recent weeks, might be considered too raw, even though he is most comfortable as a central player.
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It has been clear to see that Jesus has an impact on both the team and the community.
Many in the Arsenal squad have spoken about how the Brazilian forward and his teammates brought a winning mentality to City over the summer, while Jesus has been the player for the big moment with five goals and three assists in his first 10 games.
Eddie Nketiah would take up the mantle if Jesus were to leave the team. Despite scoring five goals in seven league games at the end of last season, he has struggled to challenge Jesus for a starting spot since the summer.
Nketiah has two goals in three Europa League group stage matches so hasn't lost his sharpness, as well as an impressive Saturday Night Football appearance where he played alongside Jesus in a front two.
At centre-back, Gabriel and Saliba have always been present, with Ben White pushing out to a right-back role.
With so many options at right-back, the chance to move White back into the centre gives them some flexibility if one of them needs a rest or a spell on the treatment table.
If Arteta wants to keep White on the right, then only Rob Holding can come in. Holding has been at the club for six years, but he doesn't have the quality of his teammates. The risks that come with Holding are shown in the red card he received against Spurs.
Ramsdale has an excellent record when it comes to avoiding injury, but his back-up has been weakened this year.
When Ramsdale was unavailable last season, Bernd Leno took on the gloves and while Matt Turner has enjoyed a run in the Europa League, question marks remain over how comfortable he is with Arteta's possession based style at the back.
A repeat of Tierney's absence last season is unlikely because of the number of options at full back.
White's emergence as a right-back option means Tomiyasu's minutes can be managed better with additional full-back cover.
Tierney has been forced to share playing time on the left side with Tomiyasu and Cedric having experience covering on the opposite flank if needed.
Emile Smith Rowe and Elneny will be back from injury in time for the World Cup, which will add to the number of players in the middle of the field.
The hiatus will allow many senior figures to recover, as only a few regulars are guaranteed to play in the tournament.
The likes of Xhaka, Partey and Tomiyasu are guaranteed to go to the World Cup and play every game for their countries, but the same can't be said for others.
The January transfer window will be used to address any depth concerns that may arise.
Given the nature of the campaign, it's hard to say what the mid-season tournament in Qatar will mean for any of the teams in the league.
There will be a contingent from Manchester City in the Middle East.
The only thing that can happen is for the team to get to the middle of November in this vein of form.
You can watch the game on Sky Sports.
Sky Sports has live coverage of the Saints in the premier league.
October 27 is the date of the Europa League.
October 30th is the day of the premier league.
November 3 is the date of the first round of theEuropa League.
The A team is in the premier league.
The Carabao Cup will be held in November.
Sky Sports broadcasts Wolves in the premier league.