Chelsea, energised by their 4-2 win over Tottenham in last weekend's FA Cup semi-final, on Tuesday got two goals from Diego Costa, who had gone seven matches without scoring, reports Xinhua news agency.
Tuesday's contest marked a return to form for Chelsea after looking flat in their previous Premier League match, a 0-2 away loss to Manchester United.
Chelsea took a 1-0 lead just five minutes in, when left winger Eden Hazard converted at the end of a play that began with a perfect long ball from attacking midfielder Cesc Fabregas.
Despite conceding early, the Saints kept their composure and were rewarded in the 24th minute with an equaliser, delivered by Oriol Romeu when the Chelsea defence failed to clear the ball after goalkeeper Thibaut Coutois turned aside a shot from Manolo Gabbiadini.
The Southampton goal was followed by a spell of end-to-end play that saw chances for both sides.
But the decisive moment came in first-half stoppage time, courtesy of Chelsea stand-in captain Gary Cahill, who connected with a header amid a scramble in front of the Saints' goal to put the hosts up 2-1.
Costa broke his scoring drought in the 53rd minute, heading in a perfect cross by Fabregas -- the Spaniard's 103rd EPL assist -- to widen the lead to 3-1.
A fine play by Hazard and Pedro led to Costa's second goal, in the final minute of regulation, while Ryan Bertrand managed to score for Southampton in stoppage time.
"We passed a big psychological step after the defeat to United because we lost three points and then we had to prepare for a semi-final against Tottenham and another tough game in the league. I think we have had a really important test and our answer was very good so for this reason I must be pleased," Chelsea head coach Antonio Conte said, as posted on the club's website.
"We must think the (title) race is open.We are ready to fight until the end and we must be proud of what we are doing this season. It's normal we have to push to try to keep this position until the end."
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
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