The Blues had taken the lead just before half-time when Ben Chilwell hit a sweet strike into the roof of the net. They didn’t extend their advantage and faced relentless pressure from the Bees as the game wore on. But Mendy denied them time after time to earn all three points.
Brentford went into the match full of confidence. They were unbeaten in their last three Premier League games and drew 3-3 with Liverpool last time out at home.
Chelsea were motivated by the knowledge that three points would take them back to the top of the table after Liverpool and Man City had climbed above them earlier in the day.
After a steady opening 20 minutes, which featured Romelu Lukaku sending a free-kick from a dangerously-close position just wide, the game sprung into life.
The Bees, who had scored five goals from set pieces so far this season, had a corner cleared which was returned into the box.
The ball was headed down to Bryan Mbeumo. The forward struck it into the ground and his shot bounced up and onto the post.
Wasting no time, Chelsea counter-attacked. Timo Werner raced down the left and crossed to Lukaku who flicked the ball home. However, he was in an offside position.
Another free-kick was awarded Chelsea’s way and the responsibility this time fell to Mateo Kovacic.
The midfielder’s effort from 30 yards out was deflected off the wall and had David Raya scrambling, but it went over the bar.
The Blues went close again when Werner fired over from range after Lukaku had held the ball up well for his strike partner.
At the other end Malang Sarr made a crucial tackle to dispossess Mbeumo who had latched onto an Ivan Toney flick on.
Chilwell continues purple patch
Then right on the stroke of half-time, Chilwell scored a beauty to put his side in front. The ball fell to him just inside the box and he hit a strike which flew into the top corner. It was the England international’s third goal in as many games for club and country.
Chelsea took control of the match after the restart. But Toney did his best to disrupt their rhythm when he could.
Lukaku had his blushes spared by the offside flag after missing a sitter from just a few yards out.
The Bees pushed for a way back into the game. They had a good chance when the ball fell to Toney on the volley. He forced Mendy into a reflex stop.
The Chelsea ‘keeper was helpless minutes later, though. The threatening Mbeumo latched onto an over-the-top ball and struck towards goal with his left foot.
It beat Mendy but could only find the post, much to the frustration of the majority of the crowd inside the Brentford Community Stadium.
The fans were up on their feet again claiming for a penalty as Trevoh Chalobah brought down Toney. But the offside flag was raised.
The pressure kept coming on the Chelsea goal. Mendy had to be quick off his line to deny substitute Saman Ghoddos from finding an equaliser.
The Blues number one was keeping his team in it and he even used his face to stop the opposition. Pontus Jansson’s strike clattered the shot stopper.
Nobody in red and white could get past him and he proved to be the difference as the 1-0 win was seen out.