One second of second-half stoppage time had elapsed in Saturday's lunchtime Premier League kick-off when the Red Devils captain twisted and turned and fired in low off the hand of Bernd Leno to spark pandemonium in the noisy away end at Craven Cottage and help ease the mounting pressure on his under-fire manager.
It was another unconvincing display from United after back-to-back 3-0 home defeats by Manchester City and Newcastle had increased the sense of crisis at Old Trafford as they made their worst start to a season for some 51 years, with growing questions over Ten Hag's future.
In a largely tepid affair that improved after the interval, the visitors had goalkeeper Andre Onana to thank for keeping the deadlock unbroken when he made two excellent quick-fire saves to deny first Harry Wilson then Joao Palhinha, whose poor clearance was partly to blame for Fernandes eventually beating Leno at the last.
The only notable moment of a bleak first period - in which Fulham fans continued their protests against ticket-price hikes after a pre-game march - saw Scott McTominay blast home from close range after a free-kick was turned back inside the six-yard box at the back post by Alejandro Garnacho after Fernandes had been cut down by Portugal team-mate Palhinha.
However, after a lengthy VAR review that lasted for four minutes, referee John Brooks was sent to the pitchside monitor and the goal was eventually chalked off after an offside Harry Maguire - who sustained a head knock early on - was ruled to have been impeding Fulham striker Rodrigo Muniz, whose first Premier League start of the season ended in tears and an injury after his Carabao Cup heroics at Ipswich in midweek.
Decent chances were otherwise few and far between, with United missing Marcus Rashford altogether. The England forward's decision to have a birthday party in a nightclub just hours after last weekend's dismal Manchester derby loss was lamented as "unacceptable" by his manager, with Rashford travelling to west London after a heavy knock sustained in training on Friday but ruled out after failing a late fitness test.
An important three points keeps United sixth for now before the rest of the weekend action, with Fulham left to lick their wounds after a third home defeat of the campaign that makes it three top-flight games in a row without a victory now for Marco Silva's men.