Chelsea suffered another case of the Stamford Bridge stutters as they threw away a two-goal lead to Saints.
Demba Ba, with his 14th Premier League strike of the season, and Eden Hazard had put Chelsea in firm control at the break and they seemed to be cruising to a first home victory since before Christmas.
But Rickie Lambert pulled Southampton back into the game with a header three minutes after being sent on and Jason Puncheon then equalised with a brilliant volley.
Since their 8-0 rout of Aston Villa on December 23, Chelsea have lost at home to QPR and Swansea and now drawn with Saints.
There had been no audible boos of Rafael Benitez before kick-off, perhaps because he chose to start with Ba ahead of Fernando Torres and with Frank Lampard in midfield.
But hours after Pep Guardiola announced he was taking charge of Bayern Munich, the dissent towards Benitez on the final whistle was clear.
The point for Southampton, unexpected given they were thumped 5-1 by Chelsea in the FA Cup just 11 days ago, lifts them three points above the relegation zone and they have the best goal difference in the bottom six.
In addition to starting with Ba and Lampard, Benitez brought Oscar and Gary Cahill into the side that beat Stoke 4-0.
Southampton also featured two changes, with Guly do Prado and Steven Davis coming into a five-man midfield and the Saints initially proved hard for Chelsea to break down.
There were some nice touches from the Blues but they lacked any real penetration, with Oscar shooting wide after a neat build-up from Hazard, Ba and Juan Mata.
Ramires released Ba in the wide right channel and his cross took three deflections before going behind for a corner, with Artur Boruc panicking the ball might sneak inside his post.
Chelsea began to find their rhythm but another promising build-up, started by a break from Hazard, ended with Cesar Azpilicueta shanking his shot high and wide.
Southampton engineered a chance for Jason Puncheon, who rose above Ashley Cole but he only managed a soft header back across goal before Chelsea took a grip on the game.
Almost inevitably, Lampard played a key role and Ba, who had marked his Chelsea debut with two goals in the FA Cup tie, finished.
The Chelsea captain beat Luke Shaw as he jinked his way into the box before laying the ball back for Azpilicueta to curl the cross in.
Oscar and Jos Hooiveld both went for the header and the ball deflected up for Ba, who executed an acrobatic volley to beat Boruc yet again.
Chelsea survived a scare when Jay Rodriguez pulled a long-ball out of the air with a delightful first touch and teed up Davies, who side-footed his shot wide from the edge of the box.
That scare jolted Chelsea into action. Some intricate one-touch football released Hazard down the left but Lampard saw his shot blocked before he fired wide after being teed up Mata.
Ba then headed back to Lampard, who lifted the ball into the box towards Hazard and Oscar, who got in a muddle but still forced Boruc to tip it round the post for a corner.
And when Southampton made a hash of clearing their lines, Chelsea pounced for the second. Ramires rifled a shot off the post but Hazard followed up to drill a left-footed shot past Boruc.
The second half started in stalemate. Southampton may have feared a repeat of their FA Cup drubbing and were keeping things tight and Chelsea were comfortable in the lead.
But the onus was on the visitors and manager Nigel Adkins threw on Lambert for Rodriguez after 55 minutes. Three minutes later he had scored.
Nathaniel Clyne escaped the attentions of Hazard down the right and swung in a deep cross for Lambert, who found space between three Chelsea defenders to head past Petr Cech for his 10th league goal of the season. No Englishman has scored more.
Chelsea suddenly looked a bit nervous at the back. The Blues had chances to wrap up the game but Ba rifled a spectacular volley over the top and Lampard curled a free-kick wide.
And then, with 15 minutes remaining, Southampton equalised.
Luke Shaw charged 50 yards down the left and pulled the cross back for Puncheon, who teed the ball up with his first touch and powered a volley past Cech with his second.
Chelsea sent Torres on for Lampard to a chorus of boos. The Spaniard rifled one good chance wide and then lofted a cross straight behind for a goal-kick.
The crowd's reaction to him was echoed by their reaction to Benitez. All is not well at Chelsea.