Southampton secured a vital point that looks to have ended Arsenal's hopes of retaining their Premiership title.
The Gunners were coasting at half-time, a goal and an extra man to the good.
David Prutton was dismissed after two rash tackles and within minutes Arsenal had taken advantage, Freddie Ljungberg tapping in a Thierry Henry cross.
But Robin van Persie's sending off gave Saints a chance and Peter Crouch pounced on it, heading home a Jamie Redknapp corner on 67 minutes to level.
It was the least Saints, and their goalkeeper Paul Smith, deserved against an Arsenal side whose season seems to be unravelling.
They started without a host of regulars and by half-time Robert Pires was added to that list.
A dour first half came to life with Prutton's sending off.
He came through with a clattering challenge on the Frenchman, a similar tackle to one he had made only 10 minutes earlier on Matthieu Flamini.
After consulting his linesman, referee Alan Wiley was left with little choice but to show a second yellow card - a decision that disgusted Prutton.
He pushed Wiley out of the way before launching a verbal attack on the assistant and was eventually dragged clear by manager Harry Redknapp.
Arsenal immediately took advantage of the first Saints red card of the season.
A passage of keep-ball culminated with an Ashley Cole shot that broke to Henry in the area. He twisted and turned with two defenders in attendance before squaring a pass to Ljungberg to score.
Arsene Wenger had initially gambled by bringing in Philippe Senderos to partner Pascal Cygan in central defence, shifting Kolo Toure to right back.
In a frantic first five minutes it seemed as if the risk would prove costly, but, despite being unconvincing, they held firm.
With the extra man it should have been feet up time for the Gunners back four.
But Van Persie's late tackle on Graeme Le Saux made sure their comfort zone did not last long, and after an earlier yellow card it made it 10 against 10.
Saints were given their lifeline and they profited through Crouch, although a superb Smith save from Henry was equally crucial when the score was still 1-0.
At the other end Jens Lehmann went walkabout when Redknapp sent in an inswinging corner and Crouch stood tall against the new-look defence to head in the equaliser.
Wenger's gamble had failed, in no small part due to Van Persie, but it was Smith who ensured Saints picked up a point in their fight against relegation.
With Arsenal piling on the pressure he tipped over a Ljungberg header and palmed away a low Cole shot.
And when he was beaten by a Cole header late in injury-time Saints were saved by the linesman's flag, the left-back having drifted offside.
Southampton boss Harry Redknapp
"I can't defend anything he (David Prutton) did. He's made two stupid rash tackles and it's totally irresponsible.
"He had no reason to tackle Pires and it was a foolish thing to do.
"I didn't see him push the ref but if he did it will be shown on TV. I saw him arguing and that's why I went over to drag him away."
Arsenal manager Arsene Wenger
"It is disappointing but we have to fight on.
"I told Van Persie at half-time the referee would be under pressure having sent off a home player to square up matters and he was an obvious target.
"I cannot support Van Persie in this but I feel we had the minimum reward for a good performance today."
Southampton: Smith, Delap, Lundekvam, Jakobsson, Bernard, Prutton, Redknapp, Quashie, Le Saux (Telfer 72), Camara (Phillips 85), Crouch.
Subs Not Used: Higginbotham, Poke, Davenport.
Sent Off: Prutton (45).
Goals: Crouch 67.
Arsenal: Lehmann, Toure (Eboue 75), Senderos, Cygan, Cole, Ljungberg, Vieira, Flamini, Pires (Clichy 45), Henry, Van Persie.
Subs Not Used: Taylor, Lauren, Aliadiere.
Sent Off: Van Persie (52).
Booked: Van Persie.
Goals: Ljungberg 45.
Ref: A Wiley (Staffordshire).