Of course, statistics are mere numbers and it will require more than a few records equalled, or even surpassed, for this millennium- edition team to be considered in the same breath as that fine vintage of a generation ago. And despite another impressive statistic - four goals against a team also challenging for a European spot - there is some way to go yet, as O'Leary recognised.
"We didn't play to our maximum but we showed character and won well," he said. "We need to compete with the likes of Manchester United's young stars, and maybe today we showed that our own young side are developing."
Even though they are marching confidently towards Europe and are, to Elland Road optimists at least, still in with a shot at the big prize, Leeds were not the finished item as they demolished a lacklustre Derby.
Lacking the biting influence of David Batty, who was absent through illness, passes too often failed to reach their intended targets and there was too little vigour when seeking to reclaim the ball.
They would no doubt argue that with such a clear advantage they could afford to be more generous than usual with their opponents - but this attitude will not, ultimately, serve them well at the highest level.
However, they overcame the handicap of an early goal against them and enjoyed a first-half romp before settling down for a victory, the margin of which barely reflected their dominance.
Derby may point to their lack of seven first-team regulars and cite this in defence of their dismal display. But the sight of Lars Bohinen sulking when substituted after a poor game must make their manager, Jim Smith, question the endurance credentials of his charges. His own European dream, while not yet shattered, is looking fragile. And it had all started so well when Derby's Vassilis Borbokis, making his full debut, darted into the box only for Lucas Radebe to take the Greek import's legs as he was shaping to cross.
Francesco Baiano struck the penalty low to Nigel Martyn's right with the keeper heading the other way. But Smith felt the bright start may have hindered his team. "It was possibly too early because after our goal they just overran us," he said. Leeds did indeed raise their game with David Hopkin and Lee Bowyer blending their power and creativity to carve openings.
The deserved leveller came when Jimmy Floyd Hasselbaink, against the grain of a performance in which he appeared to be in a team of his own, crossed low to Bowyer who clipped a gently arching low strike past the stretching Mart Poom. But Hasselbaink justified his solo endeavours when a free-kick routine on the edge of the box led to him striking venomously past a displaced defensive wall and well beyond Poom's grasp.
Deriving even further benefit from the passing part of the beautiful game, he controlled on the edge of the box to feed his Dutch compatriot Willem Korsten who, under pressure, made it 3-1 from close range.
From that point, the flood of goals dried up until Ian Harte sealed victory after launching a right-footed drive from the edge of the Derby box five minutes from time.
But Leeds could hardly claim this to have been a great performance and the young heroes will only gain their stripes when they can go for the kill with ease. In reality, Leeds should have scored more. Smith's men barely saw the whites of Martyn's eyes and even before Igor Stimac's departure through injury his defence was patchily organised and creaked each time it found itself under any kind of pressure.Reuse content