The England Under-21 international spent half a season on loan at Elland Road back in 2020 before being cast aside by the Argentine.
However, the 22-year-old secured a small slice of revenge as he scored the second in Arsenal's routine win, but only by the finest of margins.
The Whites actually belied their poor Premier League form and started the game on the front foot, forcing Bernd Leno into a series of smart saves early on.
Daniel James was sent clear by Diego Llorente and forced the German into a close range save, before a Jack Harrison drive sent the Gunners' second-choice shot-stopper sprawling.
Yet Leeds failed to deal with the returning Callum Chambers as he scored his first goal for three months just 23 seconds after being introduced as a substitute to head home from a corner.
Bielsa would have been left fuming as he watched Nketiah then chase down a wayward Liam Cooper header, before rounding Illan Meslier and finishing from a tight angle.
It would be fair to say the Arsenal academy graduate has struggled to kick on at the Emirates, but there is no doubt Bielsa's comments in 2020 would have hurt after seeing a loan spell cut short after just 19 appearances.
"Nketiah arrived here because Leeds was the ideal place to grow, because it was me who was going to coach him," Bielsa said. "I know who I am and I don't believe those messages. Everything around the transfer of Eddie was a lie, Nketiah came to play. In any way. He didn't play and he left.
"But even worse, because I, in two situations, I put Bamford on the bench and in two months he was with us, he wasn't able to play. Players do preseason. One player in six months plays two matches, thinks he will arrive to one club and play is underestimating what Leeds is as a club, a team and an institution."
Nketiah has seven goals in eight appearances in the Carabao Cup for both Leeds and Arsenal, yet Andy Townsend fears as though the youngster is not ready just yet to usurp his more senior colleagues at the Emirates.
He said on talkSPORT: "I don't think Eddie is ready yet to be a threat to Aubameyang and Lacazette for those starting spots.
"But you can't ignore the fact he keeps scoring in these competitions and he did really well for his goal."
The Gunners march on to the quarter-finals, while Leeds will have to arrest this dramatic slump in their second season back in the top flight.