After beating Ipswich Town 2-1 in their last league trip, Southampton had the chance to claim their first pair of successive away PL wins since June 2020.
An out-of-form Chelsea side perhaps presented an opportunity for the struggling Saints, but by the time the half-time whistle blew, the contest was practically out of their reach.
Enzo Fernandez twice slipped in Cole Palmer, who miscued his first effort before firing straight at Aaron Ramsdale, failing to end a now seven-game Premier League goal drought.
Fortunately for the hosts, the deadlock was soon broken from the resulting corner when Tosin Adarabioyo’s header fell kindly for Christopher Nkunku to turn in at the back post.
At the other end, Filip Jorgensen made a big save to push away Paul Onuachu’s header in what proved to be a rare Southampton attack.
Minutes later, the Blues doubled their advantage through Pedro Neto, who fired past Ramsdale after a darting underlapping run opened up the Saints.
Firmly in control, Chelsea added a third goal before the break, with Neto involved again, this time gifting Levi Colwill an early birthday present with a set-piece delivery that set up his first goal of the season.
Chelsea remained on top after the restart, although Enzo Maresca’s side lacked their clinical touch as several chances past them by.
Fernandez created yet another opportunity when he picked out Nkunku, but the French international couldn’t direct his header on target.
Still missing his shooting boots, Palmer then sent a bouncing ball high over the bar before Jadon Sancho’s neat turn freed up Neto, who mis-controlled in a promising position.
Eventually, the hosts added to their first-half lead with a fourth and final goal 12 minutes from time.
A swift counter-attack ended with substitute Tyrique George squaring for Marc Cucurella to fire home.
The late introduction of 17-year-old Shim Mheuka capped off a pleasing night for Chelsea, who move back into the top four with this result, at least for the time being.
After conceding nine times to the Blues across their two Premier League meetings this season, Southampton will be pleased to see the back of them.
Their concerning goal difference takes yet another hit, but in truth, that will likely make little difference as Ivan Juric’s side remain rock-bottom on nine points, 13 adrift of safety.