Chelsea kept pace with the leading pack in the Premier League as they moved into fourth place with an impressive win at Southampton.
The Blues took the lead when Eden Hazard capitalised on poor marking before cutting inside Steven Davis and powering a shot through the legs of keeper Fraser Forster.
Southampton had plenty of the ball but could not find a way through a well-drilled Chelsea, who looked the more threatening and went close when strikes from Hazard and Diego Costa were saved.
Costa, however, beat Forster at full stretch with a wonderful curled effort from 22 yards.
Victory was Chelsea's fourth in a row in the league - a feat they last achieved in April 2015 - and put them one point behind Manchester City, Arsenal and Liverpool.
Eden Hazard was the 2014-15 Premier League player of the season during a campaign in which former Chelsea manager Jose Mourinho said the Belgian had outperformed Real Madrid forward Cristiano Ronaldo.
Hazard struggled to maintain those heights as he struggled last season - managing just four goals and rarely showing the pace and trickery that had made him such a threat.
This season is a different story. He has already scored five goals and looks like he has regained the confidence to tease and torment defenders.
He showed skill and power with his goal at St Mary's, scoring in three consecutive Premier League games for the first time, then provided the pass from which Costa added Chelsea's second.
Chelsea were exposed defensively in consecutive league defeats by Liverpool and Arsenal this season but, since then, they have kept four clean sheets and scored 11 goals.
Manager Antonio Conte's move to a formation with three centre-backs is helping his side look more secure at the back and threatening in attack.
The Italian also appears to have implemented the sort of defending for which his country is famous, as an organised Chelsea denied Southampton's players any space in or around the penalty area and closed them down with aggression throughout.
"We've worked hard in training," said Chelsea defender Gary Cahill. "We've worked hard on the shape that the manager has brought and we are getting the rewards.
"It's OK having the shape but it's about having the mentality of the players to go out and dig in and do the business when you need to."
Southampton, whose most recent defeat at home in the league came against Chelsea in February, again had little answer to the Blues.
Saints had 55 shots on target this season before the game, but could muster only one on Sunday despite enjoying 55% of possession.
Their sole effort was Dusan Tadic's low effort, which was comfortably palmed wide by keeper Thibaut Courtois.
Southampton's chances were fleeting and, when they did come, striker Charlie Austin put one header wide and another high.
Southampton manager Claude Puel: "We played very well in the first half with so many possibilities and good play.
"But it's difficult to play against this team when you concede a goal after a few minutes. They can play their game with a strong defence and counter-attack.
"It was difficult to find solutions. It's a disappointment because we tried to play good football. We can do better."
Chelsea boss Antonio Conte: "We knew today was a test against a strong side in good shape and form. It's important to win games like this - people can increase their confidence and will to work and trust in the work.
"We created many chances. It's the perfect game when strikers score and defenders don't concede. The players deserved this; they work hard in training.
"When you see this type of game and commitment from your players, it's fantastic for a coach."
Southampton are at home to Inter Milan for a 20:05 GMT kick-off on Thursday, 3 November before a league game at Hull City at 14:15 on Sunday, 6 November.
Chelsea host Everton in the 17:30 kick-off on Saturday, 5 November.