Olivier Giroud headed a late equaliser as we snatched a point on the south coast.
The France striker came off the bench to nod Alexis’ cross past Fraser Forster - his 17th goal as a substitute in the Premier League.
Like last weekend, we started slowly. And like last weekend, we fell behind to an early goal.
A poor ball out of defence was seized upon by Austin. He found Dusan Tadic and a return pass sent Austin through for a confident finish past Petr Cech.
Austin was finding space too easy to come by and we needed a smart stop from Cech to deny him a second after Nacho Monreal got caught out of position.
Austin hit the post as our sluggish start continued, but slowly we worked our way into the contest.
Alex Lacazette looked the most likely to break through, his quick feet and sure touch catching the eye, and Forster was lucky that one sharp shot on the turn went straight at him.
But there was nothing lucky about Forster’s brilliant low save from Aaron Ramsey’s first-time shot from the edge of the box.
Southampton were happy to defend deep while Pierre-Emile Hojbjerg and Oriol Romeu shut down space in front of a disciplined back five.
That made it harder for us to pick our way through and eventually Arsene Wenger surrendered a defender to bring on Danny Welbeck and then Giroud.
Jack Wilshere also came on but Southampton should have scored again when Ryan Bertrand went through on goal.
Monreal curled one effort wide and Alexis saw a free-kick pushed away by Forster.
Then Giroud had the final word.
HOW IT HAPPENED
WHAT IT MEANS
This draw leaves us in fifth place in the Premier League - leading Tottenham on by just one point and trailing Liverpool on goal difference.
We’re back in Premier League action on Wednesday with a visit to the London Stadium to face West Ham.
Then we’re back on home soil on Saturday when Newcastle visit the Emirates.
Alex Lacazette looked sharp against Southampton - especially in the first half. These were his brightest moments:
17 - Lacazette stays strong inside the box to hold off a defender and spin to get an instant shot away. It’s straight at Forster.
18 - Alexis leads a promising break and finds Lacazette. He swaps passes with Ramsey but needs a touch to line up his shot - and Hojbjerg intercepts.
40 - Alexis pings a crossfield pass to Bellerin and his low ball into the box is hit first time by Lacazette, under pressure from Yoshida.
Copyright 2018 The Arsenal Football Club plc. Permission to use quotations from this article is granted subject to appropriate credit being given to www.arsenal.com as the source.