Nasukawa (8-1, 3 KOs) was hunting a redemptive display after being outboxed by Takuma Inoue for the WBC title in November, two-weight world champion Estrada (45-5, 28 KOs) meanwhile sought an impressive scalp in a third weight division after winning, then defending unified world titles at flyweight and junior bantam in years gone by.

Estrada, who turns 36 on Tuesday, wanted an early birthday present but time waits for no man — just ask Nonito Donaire — and much like was the case against Inoue, Nasukawa imposed himself with a busier opening early on, punctuated by sharp counterpunching. This time, there was little let-off and he remained composed throughout.

Having enjoyed a few encouraging spells of pressure in rounds two and three, Estrada let his hands go in the opening minute of the fourth as Nasukawa's defenses were put under duress.

The round-by-round scoring could've gone either way depending on what you preferred to see, Nasukawa's footwork and workrate or Estrada's cleaner punching as he crept forward to close the distance.

Two judges had it level through four rounds, the other giving Nasukawa a 39-37 advantage as they headed into round five, where Nasukawa began adding more punch variation while Estrada steadily found his rhythm to match him punch-for-punch in their close-range exchanges.

However in the sixth, Estrada's luck turned drastically.

An accidental clash of heads was compounded by him simultaneously absorbing a body shot, with Nasukawa wheeling away to prematurely celebrate before it became clear things were awry.

While a knockdown was correctly not scored by veteran referee Michael Griffin and 'El Gallo' given time to recover, his 27-year-old foe pushed his foot on the accelerator, chaining together combinations and pushing the pace in search of a stoppage.

A straight right hand and uppercut in the final half-minute were among Nasukawa's best shots late in a dominant seventh, as Estrada looked weary between rounds and you wondered whether he'd be withdrawn for his own good if punishment persisted.

77-75, 78-74 and 79-73 were the scorecards read out on the tannoy through eight rounds, Nasukawa couldn't miss behind his left hand to the body while right uppercuts were often finding a home as the home favorite utilised his physical advantages well again in the ninth frame. He wouldn't know it, but that would be the night's final action.

Estrada, still wincing around his eye from the head clash, had shipped punishment and didn't worry the younger man in the power department, so a mercy stoppage felt the right ending three rounds shy of the finish line.

The result means Nasukawa is now in-line for an immediate Inoue rematch, assuming the 30-year-old makes a successful first title defense against another legend seeking history up a division in four-weight world champion Kazuto Ioka (32-4-1, 17 KOs) on the Naoya Inoue-Junto Nakatani undercard come May 2.

The event's chief support bout ended prematurely, just 22 seconds into the second frame after former world champion Pedro Guevara (43-5-2, 22 KOs, 1 NC) was down in a heap on the canvas, writhing in agony.

Although not immediately clear what caused the issue, replays showed an accidental head clash saw the Mexican floored after lunging to throw a punch at The Ring's No. 4-rated contender Tomoya Tsuboi (3-0, 2 KOs, 1 NC).

It missed but they came together, crashing into the 36-year-old and after a few moments, it was clear he couldn't continue.

Esteemed amateur Tsuboi, who has made an impression since debuting last March, is ranked No. 1 with the WBC and WBO, with Ring and three-belt unified champion Jesse 'Bam' Rodriguez owning both world titles.

Bantamweight: Jose Calderon MD10 (95-95, 96-94, 96-94) Katsuma Akitsugi

Lightweight: Keita Kubotera KO5 (0:59) Crisaldy Beltran