Instead, Ben Chilwell’s first-half strike was enough secure a vital win for Chelsea that keeps them a point ahead of Liverpool, who had briefly moved top earlier in the day.
By the time Mendy had tipped Christian Norgaard’s overhead kick onto the bar late on, Brentford manager Thomas Frank could only shake his head in disbelief.
By that point it was clear that Mendy was simply not going to be beaten.
He had already repelled the home side’s onslaught – parrying Ivan Toney’s snap shot from close range, sprawling at the feet of Saman Ghoddos and using his face to block Pontus Jansson from point-blank range.
On the occasions Mendy was not there, he could thank his post for twice denying Bryan Mbeumo and Trevoh Chalobah for a goal-line clearance from Norgaard.
If it sounds like Chelsea rode their luck, they certainly did. On another day this could have been a humbling defeat.
Instead it was a victory that further showcased their resolve, coming despite Thomas Tuchel having to name a makeshift defence in the absence of the injured Antonio Rudiger and unavailable Thiago Silva, who only returned from international duty a day earlier.
Brentford were outstanding – but that was no surprise to Tuchel, who had warned his European champions that the home side would be in ultimate giant-killing mode.
Just ask Arsenal and Liverpool about their experiences here to know how valuable this win was for Chelsea.
Brentford seem to come to life under the lights – stunning Mikel Arteta’s side in the opening game of the season and holding Liverpool to a 3-3 draw at this venue last month.
In another late kick-off they took time to find their flow against Chelsea – but when they did, it must have felt like an irresistible force to the visitors’ defenders, who pushed ever further in retreat.
Fortunately for them, they had an immoveable force in Mendy, who came up with one stunning save after another to keep Brenford at bay.
What a baptism of fire for Malang Sarr, making his first Premier League appearance and impressing hugely. Likewise Chalobah, who continues to look so at home whenever called upon.
Playing either side of Andreas Christensen, this was an inexperienced rearguard that was a testament to Tuchel’s defensive drills on the training ground.
Different faces, but the same stubborn resolve that has been Chelsea’s hallmark since the German’s arrival.
But credit must go to Brentford’s refusal to give up and the sheer number of times they forced Mendy into action is evidence of the trouble they caused Tuchel’s side.
They could have taken the lead early on when Mbeumo fired against the post following a corner.
Chelsea had been sluggish, despite Tuchel’s pre-match warning, but after being saved by the woodwork immediately burst up the other end, with Romelu Lukaku flicking the ball into the back of the net from Timo Werner’s cross, only for the offside flag to be raised.
The roles were reversed later as Lukaku laid off to Werner on the edge of the area. The Germany striker took his time and picked his spot with the whole goal to aim for, but got his angles all wrong when firing high and wide.
It was a poor miss from a player who has been in such encouraging form in recent weeks and typified Chelsea’s attack on the day.
On too many occasions, Lukaku’s final ball missed its mark, while Werner’s decision-making let him down.
With the two strikers toiling, it took Chilwell to show them the way with a brilliantly-executed half-volley on the stroke of half-time to break the deadlock.
N’Golo Kante shifted the ball to Cesar Azpilicueta on the right of the box and he lifted a cross into the centre, which eventually fell to Chilwell, who arrived late and swept a shot into the top corner.
It was a rare moment of quality from Chelsea from an attacking perspective and should have provided a platform to build from.
Instead, it merely gave them something to defend as Brentford threatened to overrun them in a frantic final 20 minutes.
Even amongst all of that, Chelsea could still look to a key decision that went in their favour when Chalobah hauled down Toney in the penalty area, only for the offside flag to be raised.
Replays suggested the Brentford striker was onside.
But in the form Mendy was in, would anyone have doubted his ability to pull off another crucial save?