The hosts' £106.5million deadline-day signing was kept largely subdued as Potter's team failed to substantially improve upon their mid-table Premier League position and saw their indifferent form extend to one win in six in the competition.
Fulham proved it is not necessary to spend in excess of £500m to sit in the upper reaches of the top flight, with Marco Silva's well-drilled team making the hosts look toothless at times at the end of a week in which they broke the British transfer record to land Fernandez.
It leaves Chelsea stranded in ninth and already struggling to hold on to the optimism generated by owner Todd Boehly's whirlwind £315m investment during the January transfer window.
The visitors nearly opened the scoring in the 25th minutes with the game's first chance, Andreas Pereira collecting the ball in a central position and, after a deft first touch, bringing a fingertip save from Kepa Arrizabalaga with a low drive towards the corner.
It was a let-off for Chelsea, whose defence had afforded Pereira too much space. Within minutes they nearly took advantage of their good fortune, Mason Mount sweeping a cross into the box which was lifted high over the bar from six yards by the stretching Kai Havertz.
Then, on the stroke of half-time, Chelsea's moment looked to have arrived. Hakim Ziyech, fresh from his failed move to Paris St Germain on deadline day, clipped a searching ball in behind Fulham for Havertz to run onto, but the makeshift number nine could only watch as his lobbed effort drifted over Bernd Leno and came back off the post.
Fulham had enjoyed the best of the first period with debutant Fernandez largely kept quiet, and Potter responded by withdrawing Mykhailo Mudryk at the break and sending on fellow new-signing Noni Madueke for his debut.
But the immediate rewards for Chelsea were few, the second half continuing in a vein in which Fulham more than held their own against the hosts' expensively assembled creative cavalry.
Willian, a two-time Premier League winner during his days at Stamford Bridge, evaded the otherwise impressive Benoit Badiashile and broke forward down the left. However, his far-post cross was slightly too wide of Bobby Decordova-Reid, whose shot was easily saved by Arrizabalaga.
The moment Chelsea fans craved almost arrived with 20 minutes remaining. Fernandez showed the initiative that had been missing from the home side's attack to whip a spectacular first-time effort shot beyond Leno's dive and fractionally past the post. The crowd rallied, and Chelsea started to take control.
Yet for all the talk of the Argentinian, it was £10million substitute David Fofana who came closest to winning it for Potter's side, going through one-on-one against Leno before slipping beyond the goalkeeper - only to see his effort cleared off the line by the covering Tim Ream.
It was to be Chelsea's best - and last - chance as the opportunity to leapfrog Fulham into the top six and keep the celebratory mood alive slipped away.