The Blues are now on 28 points from their opening 14 matches of the season, seven points behind leaders Liverpool, while Southampton's struggles have continued, with the Saints bottom of the division on five points, seven points behind 17th-placed Crystal Palace on the same number of games (14).
A lively opening 17 minutes at St Mary's produced three goals, with Axel Disasi heading Chelsea into an early lead from an Enzo Fernandez corner, before Joe Aribo converted a cross from Kyle Walker-Peters to make it 1-1.
The Blues were back ahead just six minutes after the leveller, though, with Christopher Nkunku finding the back of the net after a horrible mistake from Southampton goalkeeper Joe Lumley, who misplaced a pass while out of his goal, and Noni Madueke found Nkunku, with the Frenchman on hand to send his side back into the lead.
Madueke then got his name on the scoresheet in the 34th minute, picking out the bottom corner with an excellent finish after being found by Joao Felix, with Southampton staring at a 11th league defeat of the campaign.
It went from bad to worse for the Saints before the end of the first period, with Jack Stephens handed a straight red card, following a VAR review, for pulling Marc Cucurella's hair inside the Chelsea penalty box.
In truth, Southampton never threatened to make the second half uncomfortable for Chelsea, who added a fourth in the 77th minute through Cole Palmer before scoring a fifth in the final stages through Jadon Sancho, and the Blues deserve to be in the title argument considering their current form and performance level.
SOUTHAMPTON VS. CHELSEA HIGHLIGHTS
7th min: Southampton 0-1 Chelsea (Axel Disasi)
Chelsea make the breakthrough in the seventh minute of the contest, as Disasi heads a corner from Fernandez into the back of the net; dream start for the Blues at St Mary's, with the centre-back converting from close range.
Joe Aribo goal vs. Chelsea (11th min, Southampton 1-1 Chelsea)
There is the response; Southampton level the scores in the 11th minute of the contest, and the goal comes from Aribo, who turns a cross from Walker-Peters into the back of the net from close range.
Christopher Nkunku goal vs. Chelsea (17th min, Southampton 1-2 Chelsea)
It is raining goals here; Chelsea regain the lead in the 17th minute of the match, with Nkunku converting into an empty net after a horror mistake from Southampton's Lumley, who misplaced a pass while out of his goal and was then left in no man's land.
Noni Madueke goal vs. Southampton (34th min, Southampton 1-3 Chelsea)
Madueke was the provider for the first goal, but he is now on the scoresheet, sending Chelsea 3-1 ahead against Southampton courtesy of a brilliant low strike, and the assist this time comes from Felix.
39th min: Southampton red card (Jack Stephens)
Stephens is sent off for Southampton for bizarrely pulling Chelsea defender Cucurella's hair inside the away side's box.
The referee gives the red card after a VAR review.
Cole Palmer goal vs. Southampton (77th min, Southampton 1-4 Chelsea)
Chelsea score their fourth of the match in the 77th minute of the contest through Palmer, who converts from close range after strong running from Nkunku, with the Frenchman driving into the Southampton box.
Jadon Sancho goal vs. Southampton (87th min, Southampton 1-5 Chelsea)
Chelsea score their fifth of the match at St Mary's through Sancho, with the Englishman producing a powerful finish after being released by Malo Gusto inside the Southampton penalty box.
Sancho is now off the mark for Chelsea in terms of goals.
MAN OF THE MATCH - NONI MADUEKE
Madueke set up Nkunku for Chelsea's second of the night before scoring a brilliant third before the break, with the attacker picking out the bottom corner in emphatic fashion.
Southampton found it incredibly difficult to deal with the England international, who had seven shots in total, while he completed 28 of his 32 passes during an excellent all-round performance at St Mary's.
SOUTHAMPTON VS. CHELSEA MATCH STATS
Possession: Southampton 45%-55% Chelsea
Shots: Southampton 6-26 Chelsea
Shots on target: Southampton 4-13 Chelsea
Corners: Southampton 5-7 Chelsea
Fouls: Southampton 7-14 Chelsea
BEST STATS
WHAT NEXT?
Chelsea will be aiming to make it five straight wins in all competitions when they head to capital rivals Tottenham Hotspur in the Premier League on Sunday afternoon.
Southampton, meanwhile, will look to bounce back from the disappointing result when they head to Aston Villa on Saturday afternoon, and they will be missing Stephens following his red card against Enzo Maresca's side.
Written by
Matt Law