EPL: Chelsea Beat West Brom, Manchester City Overcome Swansea
Costa opened the scoring in the 11th minute, leaping into the air to control Oscar's left-wing cross on his chest and then slamming a side-foot volley past Ben Foster for his 11th goal of the campaign.
Diego Costa scored again as Chelsea established a seven-point lead at the Premier League summit on Saturday by comfortably beating 10-man West Bromwich Albion 2-0 at Stamford Bridge.
Costa opened the scoring in the 11th minute, leaping into the air to control Oscar's left-wing cross on his chest and then slamming a side-foot volley past Ben Foster for his 11th goal of the campaign.
Eden Hazard added a second in the 25th minute, smuggling a deflected shot beneath Foster from Cesc Fabregas's corner, before West Brom's Claudio Yacob was sent off for a two-footed challenge on Costa.
"It was comfortable, but I thought in the first half we played amazingly well. In the first half we have to be 3-0, 4-0, 5-0 up," said Chelsea manager Jose Mourinho.
"But the quality of our football was there. I don't remember seeing many times football of that dimension."
Victory saw Chelsea set a new club record of 12 unbeaten games from the start of the season.
Mourinho's side are now seven points clear of second-place Southampton, who visit Aston Villa on Monday, and remain eight points above defending champions Manchester City, who won 2-1 at home to Swansea City.
Despite having captain Vincent Kompany back from injury, Manchester City fell behind in the ninth minute at the Etihad Stadium when Wilfried Bony finished calmly from Nathan Dyer's lofted through-ball.
But Stefan Jovetic swept home Jesus Navas's low cross to equalise 10 minutes later and Yaya Toure gave the hosts victory early in the second half after a characteristic burst into the area.
"We played very well and had a lot of chances to score the third goal, and we defended well," said City manager Manuel Pellegrini. "It was a difficult start because they scored with their only chance in the first half."
It was only City's second win in seven games. Pellegrini's side host Bayern Munich in the Champions League on Tuesday, when even victory may not spare them from a third group-stage exit in four seasons.
In Saturday's late game, Arsenal and Manchester United will both hope to make up ground on the leading sides when they face off at the Emirates Stadium.
Elsewhere, in-form Newcastle United leapt into the top four at the expense of West Ham United after recording a fifth consecutive victory with a 1-0 success at home to Queens Park Rangers.
France midfielder Moussa Sissoko settled the game in the 78th minute, finishing powerfully from Sammy Ameobi's pass to send QPR to the foot of the table.
West Ham dropped out of the Champions League places after losing 2-1 at Everton.
West Ham forward Mauro Zarate cancelled out Romelu Lukaku's early opener with a deflected shot in the 56th minute, only for Leon Osman to crown his 400th Everton appearance by sliding home a 73rd-minute winner.
Promoted side Burnley climbed to the brink of safety after following up their first win of the season at Tottenham Hotspur prior to the international break by prevailing 2-1 at Stoke City.
Danny Ings scored twice from close range inside two minutes early in the first half to put Burnley in control, with Stoke replying through Jon Walters's 32nd-minute header.
Burnley moved off the foot of the table and are now level on points with fourth-bottom Leicester City, who drew 0-0 at home to Sunderland.