If the afternoon session was chaos and collapse, the evening was restored to order by a familiar force.
As seeds tumbled all over the shop, three-time world champion Van Gerwen reminded everyone why control, timing and ruthless efficiency still win matches at this tournament.
O'Connor began brightly, settling quicker and breaking early as Van Gerwen looked slightly laboured.
The Irishman held confidently in the opening leg and twice put pressure on MVG's throw, capitalising on missed doubles to establish a foothold.
Yet the opening set turned on moments rather than momentum. Van Gerwen pinched it late with an 89 checkout in the deciding leg, a reminder of his enduring ability to strike precisely when legs appear to be slipping away.
Vintage Van Gerwen
Van Gerwen lifted his scoring in the second set, producing an 11-darter and repeatedly getting to finishes inside nine darts. A break of throw came when O'Connor missed a dart at double 14 from 148, Van Gerwen pouncing to level matters and then move ahead, his averages hovering around the ton while his opponent began to feel the squeeze.
The third set saw O'Connor break back and briefly halt Van Gerwen's momentum, checking out 76 and punishing a rare sloppy leg from the three-time champion to take the set 3-1.
There were signs of discomfort too, with O'Connor appearing troubled by something in his eye, but he powered on.
The fourth set was where Van Gerwen shut the door. A 121 checkout for a 12-dart hold set the tone, followed by a sensational 127 on the bull to break when O'Connor missed chances from 80. From there, Van Gerwen closed out the match on double 8 after surviving one missed match dart.
Van Gerwen finished with four maximums, a cluster of decisive ton-plus finishes and an average that steadily climbed as the match progressed. He faces Peter Wright-conqueror Arno Merk in the next round.
Seeded Noppert exits
In the opening match of the night, world number six Danny Noppert became the highest seed to exit this year's PDC World Darts Championship in one of the most chaotic and compelling matches of the tournament so far, losing 6-5 in a deciding set to Justin Hood after an Ally Pally classic that at times defied logic and stretched nerve to breaking point.
Hood set the early tone with fearless scoring and clinical finishing, taking the opening set 3-2 before racing into a 2-0 set lead.
The Englishman averaged over 100 in spells and flirted repeatedly with perfection, including a seven-dart burst in the second set that brought the crowd to its feet.
Noppert looked in serious trouble as his outer-ring struggles continued, and Hood missed chances only to remain firmly in control.
What followed was a staggering turnaround. Noppert found his scoring rhythm and, crucially, his timing, producing a sequence of ton-plus finishes that dragged him back from the brink.
Checkouts of 102, 126, 127 and a sensational 157 under extreme pressure transformed the contest, the Dutchman repeatedly surviving match darts and forcing a deciding set that few in the arena had seen coming.
The final set was then played at a relentless pace.
Both players continued to average north of 100 as legs were traded deep into a tie-break, Hood missing three separate darts to win the match while Noppert refused to yield.
Poised at 5-5, Hood found one last surge. A maximum and a 140 put him firmly in command before Noppert faltered with a trebleless visit at precisely the wrong moment.
Despite a brief wobble and a pause to calm the crowd, Hood returned to take out tops and finally bring the epic to a close.
Both players averaged over 102 and were over 40% on their finishing, with a whopping 19 maximums between them.
Noppert departed having produced four ton-plus checkouts and one of the great escapes that ultimately fell just short.
Hood advanced with a mighty display of darting composure, power and resilience, setting up a last 32 clash with compatriot Ryan Meikle.
Scutt troubles the Flying Scotsman
Gary Anderson survived a ferocious examination from Connor Scutt to book his place in the third round, edging a high-quality contest 3-1 in sets despite being pushed to the brink more than once.
Scutt struck first, punishing Anderson's early uncertainty on the outer ring to take the opening set 3-1.
The Scot outscored his opponent but paid the price for missed doubles, allowing Scutt to convert a 75 checkout and briefly raise the prospect of another seeded casualty.
Anderson's response was emphatic rather than immediate, tightening his finishing just enough to level the match with an 80 checkout on double five and reassert some control.
From there, the standard rose sharply. Anderson found a higher gear in the third set, producing an 11-dart leg with an 88 finish and averaging 113 across the set, part of a match average that climbed to 107 by the end. His scoring became relentless, seven 180s punctuating a spell in which Scutt was repeatedly left watching as Anderson powered through legs in five visits.
'Iffy' Anderson edges through
Scutt, though, refused to fold. The fourth set was riddled with drama, the Englishman landing six perfect darts either side of an Anderson maximum and surviving a shaved-bull match dart to force a deciding leg.
When Scutt then missed a set dart from 129, Anderson pounced, sealing the match with a nerveless 90 checkout on the bull to close out victory.
Anderson finished with a cluster of timely checkouts, including 88, 83, and that decisive 90, his experience telling at the sharp end after spells where his doubling wobbled.
"The doubles were a bit iffy at the start," Anderson told Sky Sports.
"The scoring kept going, and doubles went in at the end. It's alright!
"We are getting there. It's not quite together yet."
Anderson faces Jermaine Wattimena in round three after the Dutchman defeated Scott Williams in the afternoon session.
Rock cruises through
Josh Rock wrapped up the final match before Christmas in composed fashion, defeating Joe Comito 3-1 to secure his place in the third round of the and underlining his status as one of the tournament favourites.
Rock claimed the opening set 3-1 with measured finishing, taking out tops to close after Comito failed to convert from 125. The Australian showed flashes, including an unconventional 120 checkout via treble 20, double 20 and double 10, but Rock's control of the key moments ensured there was little reward for the effort.
Rock broke immediately in the second set, then produced the standout leg of the match with an 11-darter that featured his first maximum of the contest and ruthless setup play. By that stage, Comito was struggling to apply consistent pressure, repeatedly watching Rock return after missed opportunities at doubles.
Rock opened the third set with back-to-back maximums and briefly flirted with a nine-darter before settling for a comfortable hold, then closed out the set with a clean 100 checkout to move one leg from victory.
Comito momentarily delayed the inevitable by pinning tops from 110, but Rock's scoring remained a gear higher whenever the gap needed to be reasserted.
The match ended with a familiar pattern. Rock missed his first match darts at double 20, but Comito was unable to capitalise on a chance at 100. Given another visit, Rock made no mistake, pinning double 5 with his final dart to seal a controlled win.
Rock finished with four 180s, an 11-dart highlight leg and a series of steady, pressure-free finishes that reflected the overall tone of the contest. He will face Callan Rydz next.
Tuesday evening session results:
Gary Anderson 3-1 Connor Scutt
Michael van Gerwen 3-1 William O'Connor