LONDON - Midfielder Eden Hazard scored the only goal as Chelsea beat West Ham 1-0 at Upton Park on Wednesday to maintain its five-point lead over Manchester City in the Premier League.

Brazilian midfielder Ramires was given too much space on the right and crossed for an unmarked Hazard to stoop and nod the ball home in the 22nd minute, although replays suggested he may have been a fraction offside.

The goal came midway through the first half in a fiercely contested London derby that saw six yellow cards.

Chelsea looked vulnerable at the back as West Ham pressed strongly for an equalizer, but the league leaders still posed a threat on the counterattack.

The lively Ramires hit the upright and had a shot blocked by West Ham goalkeeper Adrian.

Chelsea goalkeeper Thibault Courtois produced several fine saves as West Ham's attackers were unable to covert a glut of second-half chances.

West Ham's Diafra Sakho will be particularly disappointed not to have been on the scoresheet, with the Senegalese striker unable to convert several free headers and also hitting the post.

West Ham defender Aaron Cresswell cleared off the line from a Willian shot while substitute Nene had a shot blocked by Chelsea captain John Terry in stoppage time.

The result keeps Chelsea clear of Manchester City with a game in hand, after a League Cup final win over Tottenham on Sunday.

"It was a great victory for us," Chelsea manager Jose Mourinho said.

"It was really difficult. When the emotion is so high, the tempo is so high, the players were so fantastic in their commitment and with their positive aggressivity."

The result sees West Ham fall to 10th in the table, with only one win in their last 11 league matches.

"We had a great performance, and we have to take a lot of positives," West Ham manager Sam Allardyce said.

"A little bit of great goalkeeping and a little bit of poor finishing was what kept the result from us."

Mourinho said that Nemanja Matic, suspended for this match, injured himself while celebrating the League Cup win, twisting his ankle on the pitch.

Mourinho added that the midfielder would be fit in time, though, for Chelsea's Champions League second leg match against Paris Saint Germain next week.