The valiant visitors will have been brimming with elation, ecstasy and relief on their voyage back down from Nottinghamshire, however, those emotions did not look close to becoming intertwined with the squad for much of the affair.
They were 1-0 down and looked off the pace; an absence of thrust and endeavour, a distinct lack of creativity and any real formula to try and dissemble the Forest backline had all made a comeback appear unlikely.
It was only in the 57th minute where their fortunes would undergo a drastic, dramatic yet delirious upheaval through Rubin Colwill's arrival on the City Ground turf, though, which may just have provided McCarthy with plenty of food for thought.
And, for the 19-year-old midfielder, a significant impact was produced in a mere 53 seconds.
Following Will Vaulks' delivery into a crowded area, Colwill latched onto the loose ball, showing intelligent positional awareness to get into a promising position and slot his effort into the Forest net.
That was his first senior goal- marking yet another triumphant milestone in what has been a fledgling, but striking career to date- but he was not done there.
With seventeen minutes to spare, he ran at the heart of the hosts' defence before unleashing a delightful strike from outside the 18 yard box, which found its way past Reds' stopper Brice Samba.
As tension swarmed the East Midlands air late on, they would display solidity as well as composure to keep their opponents at bay and return home with a 2-1 victory under their belts, providing momentum for Wednesday's trip to Coventry City.
It now means that they are positioned 8th in the league table, having lost only one of their opening six encounters and will now be looking to instil a consistent winning mentality in upcoming matches against the Sky Blues and then at home to Bournemouth.
And with preparations already heading underway in regards to the midweek clash with Mark Robins' men, McCarthy and his staff have been left with a significant decision to think about- one that could no doubt shape the outcome at the Ricoh Arena.
Rubin Colwill needs to start.
His importance to this Cardiff team
At only 19 years of age and with a very limited senior footballing curriculum attained, it is quite hard to fathom how Colwill already carries such a weight of importance at the Cardiff City Stadium.
He has shot to prominence in the blink of an eye and, after the spectacular individual showing to guide his side to three points, his progression is only upwards, leaving the Bluebirds faithful in raptures of excitement as to what he could achieve this term.
With the likes of Harry Wilson, Sheyi Ojo and even Josh Murphy no longer plying their trade in City blue- and Lee Tomlin's fitness still a pressing issue- it would be fair to say that there are now very few players at the club who can provide a creative outlet and make things happen from nothing.
Perhaps, after rocket-heeled wide man Ryan Giles, you would even say that Colwill is the only other individual that truly ticks those boxes.
In his play, he always showcases an eagerness to create and spark attacking rhythm; even if it does not come to fruition all the time, that offensive desire will no doubt bode well for a City attack often accused of lacking invention.
He often enjoys driving into deep areas in possession and running at opponents, utilising his ball-carrying ability, trickery, power and physical presence to really give the Bluebirds an additional dimension in the final third, while he is also a more-than-adept passer and can interchange well with team-mates.
It is what they need right now. Mark Harris has been deployed out wide this term, and though his endeavour, pressing and knack of creating space can be trumped by few at Cardiff, Colwill's technical supremacy means at this point in time, his inclusion in the side is paramount.
Leandro Bacuna has been stationed on the right of a front three, too, but once again, many would argue that his skill-set is not what is required in attacking positions- with the tenacious, ball-winning components of his game making the natural midfield role a more ideal fit.
Along with that, the divisive deadline day departure of Murphy on loan to Championship rivals Preston North End will have no doubt granted Colwill an increased opening to stamp down his authority on the starting eleven.
Although it can look like a huge responsibility for someone so young- and it is- he has shown time and time again that he is up to the task, consistently impressing and dazzling for both club and country.
No one will be expecting the former academy star to start each games, but he is sure to be an important cog in the system as a promotion push remains the call of duty for the current season.
Who else could mirror the trajectory?
As things stand, Colwill is the illuminated success story of Cardiff's excellent work towards paving a much clearer pathway from academy football to the first team.
But he is not the only one to benefit from the newly-adopted philosophy and there are many that could well be the next cabs off the rank before long.
Kieron Evans is currently a name collecting interest and catching eyes at an ever-accelerating degree. A diminutive winger with the ability to create, score and attack pockets of space in the final third, he is another player that followers of the club's under 23 side would believe offers something different.
It is no wonder, then, that he has earned the approval of McCarthy- just like his former academy teammate back in February.
He made his senior debut in the win over Forest, appearing as a late substitute for Welsh forward Harris, who is yet another graduate of the Bluebirds' academy system.
With a real dearth of wide options in the Welsh capital following a summer exodus, it is hoped that Evans can successfully make the transition into the senior game and impose his presence in the side over the course of the season.
Sam Bowen can be added to that list, too. He also debuted in the second-tier on Sunday afternoon as a late inclusion for the injured Bacuna, and an overall solid display will mean that he has done his chances little harm going forward.
For supporters, it is warming and refreshing to see such a transparent route for homegrown talent now- because, for what seemed an eternity, there was a lack of integration into the senior setup from academy football.
Quite simply, a vision had seemed to be implemented solely on the present as opposed to what the future could bring, which was, by all accounts, unsustainable. Given Cardiff's financial situation as a result of the hard-hitting detriments of the pandemic- which clubs all over the country are still in limbo over- there is even more facilitation for these young, hungry, gifted players to have an opportunity.
These are the foundations that Cardiff are now looking to structure themselves upon, and there is no denying that with the current influx of talent from age group level, it could really bear fruit for years to come.