The Saints thoroughly deserved the points after outplaying Chelsea in virtually every area. They were sharper, hungrier and looked the side more determined to leave the field with a win.
Inevitably question marks will be raised about Rafael Benitez's team selection, but the problems were collective rather than individual and no one player gave justice to the jersey, the club or the supporters.
From the off Southampton set about Chelsea with the sort of tempo you'd expect from a side facing relegation, but Chelsea never responded over 90 minutes.
It's not like Southampton's tactics were particularly revolutionary. They did the basics well but combined their pressing and commitment with a quality which was conspicuously lacking from the Londoners.
Do Chelsea really expect teams to let them go into their patch and stroke the ball around unopposed?
Once again, this was a game in which Chelsea started in first gear, and barely made it above second despite the importance of the result.
Victories for Arsenal and Tottenham have further congealed the scrap for a top four finish and if Chelsea do miss out, they only have themselves to blame after numerous showings like this.
With Juan Mata absent through illness, the only real first choice absentees were Ashley Cole and Ryan Bertrand, but as Manchester United demonstrated earlier on in the day, the sum should be greater than the parts.
It's also worth pointing out the cumulative cost of the two starting line-ups. Southampton's has been constructed for under £15 million and £7 million of that was on Jay Rodriguez.
But effort and endeavour cost nothing, and at the end of the week the Saints squad will be able to reflect on their pay packets with pride. Could any lavishly remunerated Chelsea player say the same?
There was no fluency to Chelsea's game and the slow tempo made it even easier for a feisty Southampton to disrupt the Blues rhythm. In addition to that, there was no desire when Chelsea didn't have the ball to get it back again, and as a result the hosts were regularly able to piece together moves to the edge of the Chelsea box and cause trouble.
The first goal epitomised everything which was wrong and right about the two sides respective efforts.
After winning a throw-in in an innocuous area down the left, Southampton quickly got the ball moving and zipped it about as Chelsea stood and admired.
Jay Rodriguez swapped passes with Steven Davis to finish smartly after 22 minutes and that was no more than they deserved after an enterprising opening.
The equaliser came courtesy of a John Terry header from Marko Marin's corner and to my immediate memory, that was virtually Chelsea's only shot on target in an hour and a half's football.
Even the goal was from a basic set-piece rather than from any inventive or intuitive football, and after Ricky Lambert's fine 30-tard free-kick restored Southampton's lead, chances were too few and too far between for Chelsea to have any genuine grievances about the outcome.
The failings were blatantly obvious but neither Benitez or the men on the pitch seemed willing or able to rectify them.
Chelsea were constantly defending too deep and that allowed Southampton time and space to construct attacks but that generosity was not reciprocated by the hosts.
Whilst Jack Cork and Morgan Schneiderlin were tenacious and energetic in midfield, Frank Lampard and John Obi Mikel failed to match that enthusiasm as the Saints took control.
Branislav Ivanovic was once again a disaster waiting to happen at the back and the uncertainty throughout the core of the team inhibited the forward players.
For large part Marin and Victor Moses were peripheral, and as the rest struggled Oscar became anonymous and the supply line to Fernando Torres was non existent.
Eden Hazard's arrival injected some class to Chelsea's play, but even still, the momentum given in the last 20 minutes when Southampton retreated could not be capitalised on, and the prospect of a second goal grew more distant as the game wore on.
If I'm relieving Benitez of blame for his initial selection, then I will be less forgiving for his substitutions. Hazard for Marin was the obvious choice to him, even though the German had looked much more effective than Moses.
Swapping Ramires for Mikel was the sort of straight swap in which Benitez has built a career on, but if anyone can explain the logic in him replacing the increasingly influential Oscar for Benayoun––whilst leaving Demba Ba on the bench throughout––I'd be thoroughly enlightened.
I'd be scraping the barrel to find positives from that performance, and indeed, after taking a moment to ponder I cannot think of any.
The only sliver of light from the whole debacle is that Chelsea still have a top four finish in their own hands, but the enthusiasm following the stylish win over West Ham has quickly dissipated and I'm now viewing the forthcoming Premier League fixture list with some trepidation.
But if we've learnt anything from Chelsea so far this season, it is that the next game usually has no bearing on the one previous, either in positive or negative terms.
With so many games in so little time to come, there is little point dwelling on a terrible day at the office, but that game fell way below the expectations of a Chelsea side and whips need to be cracked behind the scenes as a consequence.
Let me know your thoughts on today's game by posting below, or by getting hold of me on Twitter @bainesyDiego10