Jay Rodriguez's first Premier League goal since March 2014 salvaged Southampton a 1-1 draw after Jermain Defoe thought his penalty had handed Sunderland a priceless away victory.
Stand-in Sunderland goalkeeper Jordan Pickford's mistake gifted Southampton the leveller, however, as the Black Cats' deputy allowed Rodriguez's strike to slip under his body in a cruel late blow.
This was Pickford's chance to come of Premier League age after Vito Mannone's elbow injury, but the 22-year-old's error proved very costly on the south coast.
England forward Rodriguez has spent the last two years battling serious knee ligament trouble, and even in midweek new Saints boss Claude Puel suggested he could go on loan for regular match action.
The 27-year-old will insist his late goal underscores his lasting abilities however, as he hit the Premier League net for the first time since a brace in Southampton's 4-0 win over Newcastle at St Mary's on March 29, 2014.
Defoe's unrivalled sharpness so nearly sealed a vital win on the road for David Moyes' men, but in the end both sides remain winless in the league after three matches.
New Sunderland boss Moyes insisted Pickford could prove himself worthy of a regular run ahead of this clash, with Mannone now out for three months.
But the ex-Manchester United and Everton manager may well look to the transfer market to add competition among his goalkeepers now, even if Pickford can still have a bright future.
Southampton's neat start yielded no clear-cut chances, and after that initial 20-minute dominance the first half receded into mediocrity.
Tadic drove just over form 20 yards, Austin forced Pickford into a smart save and was then ruled offside when through on goal.
Lamine Kone spurned the chance of the half though, heading way over when criminally unmarked in Southampton's box.
Jack Rodwell failed to angle his approach-play header to a team-mate when Saints' defensive shape let them down again in the box just minutes later.
And then Fabio Borini failed to do justice to Patrick Van Aanholt's fine inside ball, unable to dig out a shot when twisting awkwardly.
Twice Lynden Gooch picked Oriol Romeu's pocket, hounding Saints' defensive midfielder to fine effect. On both occasions however the final ball failed to match the determination.
Austin's galling afternoon continued unabated, the sluggish striker falling prey to two quick offsides, failing to capitalise on penetrative approach play.
Borini's weak free-kick failed to trouble Fraser Forster in a rare Sunderland foray, before Redmond could not find the finish to match his scything run for the hosts.
The home crowd called for the introduction of Shane Long, and boss Claude Puel duly obliged.
Tadic proved a curious withdrawal, when everyone expected Austin to receive the hook. The former QPR hitman did indeed retreat to the bench soon afterwards however, Puel mustering all his firepower by sending Jay Rodriguez into the fray.
While Saints were tinkering however, Sunderland's far more settled set-up quickly paid big dividends.
The sharpest striker on the pitch all day, Defoe had just kicked himself for failing to pull the trigger in the box when another chance came his way.
Defoe so totally outfoxed Jose Fonte that hapless Saints' captain upended Sunderland's veteran forward in the box.
The wily Wearside man stepped and duly buried the resulting penalty.
But just when the visitors were dreaming of a precious away victory, up stepped Rodriguez to drill home thanks to Pickford's error.