The two starlets have had differing fortunes this term, but the evidence of Arsenal's 2-1 victory at the Vitality Stadium suggests that they may have a big role to play for the Londoners during the second half of the campaign.
While Nketiah shone during pre-season, he was sent on loan to Championship team Leeds United by previous coach Unai Emery, who felt that the Anglo-Ghanaian starlet would be better served by regular game time.
Seventeen games and three goals under Marcelo Bielsa later, he was recalled to the Emirates Stadium by new coach Mikel Arteta, who clearly believes the 20-year-old has a role to play - already - for the capital club.
On the evidence of Monday's showing, he may be right.
Having been handed a starting role, the youngster repaid Arteta's faith with the visitors' second goal on 26 minutes, tapping home after fine work from Saka.
Nketiah will have been delighted to have picked up where he left off following pre-season, and should have ample opportunities to prove his quality between now and the campaign's end, particularly if Barcelona do secure a late-window move for Pierre-Emerick Aubameyang.
However, while Nketiah shone, the evening belonged to Saka, who enjoyed one of his finest performances of his nascent career.
The starlet has now contributed a goal and an assist in three matches this term -- more than anyone else in the Arsenal squad -- and only Aubameyang and Gabriel Martinelli have been involved in more goals than the 18-year-old, who has been involved in 10 (three goals, seven assists).
Here, he excelled, slamming the ball past Mark Tavers in the fifth minute after fine interplay from Joe Willock and Martinelli, before contributing a delicious cross for Nketiah 21 minutes later.
"Mikel's trying to bring back the philosophy, the Arsenal passing way and I feel like we played really good football in the first half," Saka told journalists, as per the Daily Mail, after the match.
"We played some good bits of football and the goal obviously was very good."
Despite impressing as a winger in the Gunners' academy, the Anglo-Nigerian youngster continues to impress as a stand-in left-back, and deserves immense credit to adapting to a new role with such aplomb.
"That's the situation now because we don't have any left-backs at the moment," Arteta explained. "What I like is that he's put his head down, it's not his favourite position to play, but we try to adapt him with his qualities to play him as much as possible in the position that he likes.
"He is very willing to learn all the defensive principals that we are asking him to do and his attitude is very good."
Arsenal now travel to Portsmouth in the fifth round, while Kelechi Iheanacho scored the only goal of the game as Leicester City downed Brentford to progress.
Despite Semi Ajayi's 72nd-minute red card, West Bromwich Albion clung on to down West Ham United 1-0 in the biggest giant-killing of the round, while Liverpool must replay against Shrewsbury Town after the League One side's sterling second-half comeback.
Joel Matip was handed his first start for the Reds since October 20 and the 1-1 draw at Manchester United, while Jurgen Klopp also turned to Mohamed Salah late on as he sought to put the tie to bed and avoid an Anfield replay.
While the former remains on loan at Le Havre for the rest of the campaign, Toko Ekambi marked his arrival from Villarreal with a debut goal on Sunday as OL trounced Toulouse 3-0.
Maxwel Cornet and Moussa Dembele had earlier netted for Les Gones, before Toko Ekambi came off the bench to bag the hosts' third in the 77th minute for his first goal in French football since leaving Amiens in 2018.
"When you come to a new club, you dream of this," the striker told journalists after the match. "Particularly when you're an attacker, you dream of scoring the first goal, and that's what happened today.
"I'm very happy, but you have to quickly move onto the next thing, because the games come quickly."
In Lille, Victor Osimhen was ineffectual as Neymar's double fired Paris Saint-Germain to a 2-0 victory which extends their lead at the table to 10 points.
Andy Delort continued his fine run with a winner for Montpellier against Dijon, Habib Diallo was also on the scoresheet as Metz won 1-0 at Stade de Reims, while Wahbi Khazri's brace sent Saint-Etienne past Nimes, ending their four-game losing streak.
Like Toko Ekambi, The Gambia's Musa Barrow scored his first goal for a new club when he netted Bologna's second in a 3-1 victory at SPAL 2013.
The 21-year-old was recruited from Atalanta on January 17, and has wasted little time endearing himself to his new supporters.
By contrast, it was a weekend to forget for Torino's African stars Nicolas Nkoulou, Koffi Djidji and Soualiho Meite, who were complicit in an abysmal display as the Turin heavyweights went down 7-0 at home against Atalanta.
At the top of the table, Victor Moses was an unused substitute for Internazionale following his loan move from Chelsea, and the former Nigeria international watched on as they were held 1-1 at home against Cagliari.
It represents an opportunity missed for Inter, who had two players sent off, as they missed the chance to capitalise on Juventus' 2-1 defeat at Napoli.
With Ashley Young, playing on the right side, starring for Antonio Conte's side -- and weighing in with an assist -- it will be intriguing to see exactly how the Italian coach uses his former Stamford Bridge charge in Lombardy over the coming months.
There was more frustration for Thomas Partey and Atletico Madrid on Sunday, as they were held 0-0 at home by Javier Aguirre's Leganes.
The Ghana powerhouse was arguably the game's outstanding individual, creating two goal-scoring opportunities, winning six aerial battles and making six combined tackles and interceptions.
However, despite his industry, his wasteful shooting -- none of his four shots were on target -- summed up a tricky afternoon against Lega, for whom Nigeria duo Chidozie Awaziem and Kenneth Omeruo excelled.
The draw leaves Atleti 10 points off the pace, and without a league win since their victory over Levante on January 4.
Finally, to Germany, where RasenBallsport Leipzig's lead at the top of the table was cut as they were beaten 2-0 by Eintracht Frankfurt and all three of their near rivals claimed all three points.
Nordin Mukiele and Dayot Upamecano enduring a disappointing afternoon for the visitors.
Achraf Hakimi was in typically enterprising form down Borussia Dortmund's right flank as they thumped FC Koln 5-1, while Amine Harit wholly failed to impose himself as Schalke 04 were outclassed 5-0 at Bayern Munich.