Substitute Ben Chilwell dragged Chelsea to a breathless 2-1 Premier League win over West Ham with a virtuoso control and finish then an assist for Kai Havertz.
Chelsea still had to ride their luck en route to a third win in six top-flight games, however, with Maxwel Cornet denied a late leveller for West Ham.
Edouard Mendy raced out to dive at Jarrod Bowen’s feet, but his weak palm gifted Cornet the chance to lash home.
The Hammers’ wild celebrations were cut short, however, as the goal was ruled out after a VAR review.
The officials deemed Bowen’s trailing leg on Mendy a sufficient foul to disallow the goal, leaving the Blues to tiptoe to three vital points.
England full-back Chilwell only joined the fray with 18 minutes to play, but turned the game on its head.
Michail Antonio had tapped West Ham into a 1-0 lead after a low-quality opening hour.
But Chilwell then provided a majestic piece of control from Thiago Silva’s lofted pass before slotting home a fine one-touch finish.
The ex-Leicester defender then teed up Havertz to side-foot home, with the Blues expecting to see out the win before that last-ditch drama with Bowen, Mendy and Cornet.
New recruits Pierre-Emerick Aubameyang and Denis Zakaria watched on from the stands, with both men doubtless mightily relieved at this result.
Boss Thomas Tuchel branded the close of the transfer window a “fresh start” and, despite clear structural problems in this match, three crucial points will hand everyone at Stamford Bridge a major lift.
Tuchel told BBC Match of the Day afterwards: "We were lucky today to get the VAR decision in our favour, which was for me the correct decision. We want to turn the game around and keep the three points.
"They do this to every team, it is so hard to create spaces, to create chances. They defend deep and with bodies and physicality. It is hard to find a consistent rhythm, then you go 1-0 down it is almost impossible - to keep believing was very important.
"To get the opener from the bench from Chilly and then from Kai was important because we want spirit. If we have a strong bench we have a higher chance to win.
"You need be tough, I know they can do it. It is also down to the situation, the transfer window is closed, everyone knows he is in the group. We need to improve consistency and this is not over."