Saints held the league leaders at St Mary’s with a professional performance which fully merited a point.
Sadio Mané’s 17th minute opening strike was cancelled out on the stroke of half-time by Eden Hazard’s perfectly executed equaliser, but Saints protected their efforts with a solid second-half display which saw them extend their unbeaten run to three league matches.
Mané’s strike saw Chelsea concede for only the second time in the first half of a Premier League encounter in 14 matches, and Saints were close to holding that lead until the break, until Hazard’s intervention just before the break.
Morgan Schneiderlin was sent off for picking up two bookings before the 90, but Ronald Koeman’s men were good value for their point as they protected themselves against a Chelsea barrage late on.
It was the first time that Saints dropped points after taking the lead in a game this season, but it denied Chelsea a successive win at St Mary’s.
Koeman had made a handful of changes to the side that started the win over Crystal Palace on Boxing Day with Jose Fonte, Victor Wanyama, Dušan Tadić and Matt Targett all coming into the team.
Nathaniel Clyne missed out through an injury sustained in that previous game, so Maya Yoshida moved across to the right side of defence, and with fellow full-back Ryan Bertrand ineligible to play against his parent club, Targett started at left-back.
Saints got the game under way, defending the Northam stand which was partially in the sunlight, with Fraser Forster’s opposite number Thibaut Courtois having the benefit of the completely shaded area.
A predictably competitive opening to the game saw Saints survive an early onslaught from the Blues who ramped up the pressure inside the first quarter of an hour, before Saints answered those initial questions with style.
Moments after Gary Cahill had made an impeccable interception on Tadić’s attempt to find Mané inside the area, the same combination from the hosts drew the opening goal of the game in the 17th minute.
Tadić’s dinked ball over to Mané was seized upon by the Senegalese who, with Chelsea goalkeeper Courtois advancing, waited patiently to lob the ball over the Belgian shot stopper for 1-0.
Saints had a foothold on the contest, and looked to strengthen that when Morgan Schneiderlin fired a volley over on the back of a corner with the hosts going close to doubling their advantage in the latter stages of the half.
With Koeman’s men keeping tight at the back, Tadić and Mané both switched flanks further forward to good effect, but the best chance to score again came when Yoshida broke forward into the area and the ball broke to Pellè, whose snatch shot on the turn went over the bar.
Then, as two minutes went up for stoppage time at the end of the half, Chelsea produced a moment of magic to level the scores.
A measured chip from Fabregas found Hazard in space down the left flank and he cut inside to roll past Yoshida and Alderweireld to rifle home a shot into the bottom right corner for a tough to take equaliser heading into the interval.
José Mourinho made a change to his team at the break with Willian on for Schürrle, to pose Matt Targett with a new challenge for the second 45.
The Brazilian playmaker instantly added a more direct threat from the visitors, getting two bites of the cherry from shots on the edge of the area which were both charged down by the Saints defence.
Fabregas was booked for diving inside the area under pressure from Targett before Hazard fired wide, a couple of chances which prompted a second change from the hosts, with Florin Gardos coming on for Yoshida so that Alderweireld could slot in at right back.
Saints soaked up the pressure from the visitors as they began to swarm across the backline, but without working Forster, staying restricted to shots from range.
The Blues went for it by bringing on Didier Drogba in place of Mikel, and Saints followed suit with the introduction Shane Long for Steven Davis, though the hosts remained under the cosh as the match entered the final ten minutes of play.
Saints’ resilience enabled them to launch some late counter-attacks, but in doing so, were slightly open when Hazard collected the ball on halfway. Schneiderlin’s lunge on the Belgian earned him a second yellow card and an early walk down the tunnel prior to four minutes of additional time.
Loic Remy replaced Costa in attack for the visitors, but Drogba remained the target for the Blues inside the six yard box where he was ably marshalled in a nervy finale as Saints held out for the draw.
Southampton team: Fraser Forster, Toby Alderweireld, Jose Fonte (c), Maya Yoshida (Florin Gardos 62), Matt Targett, Victor Wanyama, Morgan Schneiderlin, Steven Davis (Shane Long 77), Sadio Mané, Dušan Tadić (James Ward-Prowse 58), Graziano Pellè
Unused substitutes: Kelvin Davis, Lloyd Isgrove, Harrison Reed, Jason McCarthy
Booked: Yoshida (57), Schneiderlin (72 & 89), Pellè (90)
Goal: Mané (17)
Chelsea team: Thibaut Courtois, Branislav Ivanovic, Gary Cahill, John Terry (c), Filipe Luis, John Obi Mikel (Didier Drogba 74), Nemanja Matic, Cesc Fábregas, Eden Hazard, André Schürrle (Willian 46), Diego Costa (Loïc Rémy 89)
Unused substitutes: Petr Cech, Kurt Zouma, Ramires, Cesar Azpilicueta
Booked: Matic (31), Fabregas (55)
Goal: Hazard (45 + 1)
Referee: Anthony Taylor
Attendance: 31,641 (including 3,217 away)