Brendon McCullum says the inexorable pressure of testifying against former teammate Chris Cairns played a major role in ushering his premature retirement from cricket.
Former New Zealand captain McCullum has revealed the toll that being a witness in the 2015 perjury trial of allrounder Cairns took on him in his newly released book Declared.
Cairns was acquitted of the charges, related to alleged match fixing.
Quick single: Hazlewood hungry for more in Matador Cup
That finding came near the end New Zealand's tour of Australia, during which McCullum made a decision to accelerate retirement later that summer.
He had originally planned to play at the subsequent World T20 in India but found his motivation had waned considerably following a heavily scrutinised role as a witness at Southwark Crown Court in London.
"It's impossible to ignore the fallout from the trial completely, and it's been chipping away at me like Chinese water torture right through the Australian tour," McCullum wrote.
McCullum goes into detail about his decision, revealing it came on day two of New Zealand's tour match against a Western Australian XI at the WACA.
"When it's my turn at the crease, something snaps. I run at every ball and whack a wild 49 off 28 balls. Hess [Mike Hesson] must be alarmed at what he sees," McCullum writes.
"When I charge, miss with a wild swipe and get stumped, he finds me out the back where I'm having a durry, trying to calm myself down. 'You okay?'
"'I'm done, mate,' I tell him.
"Hess knows I've been struggling, but it seems like a sudden and emotional decision. He asks me if I'm sure I want to retire.
"It is quite sudden and emotional, but I'm sure. I had visions of playing the T20 Worlds in early 2016, then giving away the shorter-format stuff for the Black Caps and just playing tests, but I've come to the end of my tether. I just know in my waters I've had enough."
A combination of on-field struggled and the strain of the Cairns trial led to the decision, McCullum explains.
"Partly it's the attritional warfare that the first two Tests have turned into, on pitches that have done nothing for the game, just inflated the averages of, mostly, the Aussie top order, who've had the advantage of batting first.
"They've been games that have tested the patience of both the players and the few spectators who've turned up to watch them, and have ground the fast bowlers into the dust, and, in Mitchell Johnson's case, into retirement.
"But it's not just what's been happening on the field.
"In the month since I gave evidence at Southwark Crown Court, the Cairns case has dragged on, a wound to cricket that keeps bleeding like a stuck pig."
McCullum goes into further detail around the trial, expressing surprise he proved to be the key prosecution witness.
He lamented how the trial was portrayed in the media as a battle between himself and Cairns - a former friend and player he first regarded as a hero.
He admits their relationship is now irreparably damaged.
Quick single: Boof open to extra selector
McCullum was one of three key Crown witness against Cairns, along with disgraced former cricketer Lou Vincent and Vincent's ex-wife Eleanor Riley.
McCullum expressed concern at the summation of Justice Nigel Sweeney, who instructed the jury to be sure of the evidence of at least two witnesses before they could convict Cairns.
Vincent was discredited by the defence as a confessed match-fixer while Riley's evidence was about alleged confessions from Cairns on a drunken night out.
McCullum wrote he did not understand why his evidence alone couldn't be enough to bring about a conviction.
He said he had wondered often since if he made the right decision to put himself through the stress of testifying - something he didn't have to do.
"I was prepared to stand up, even under pressure and under fire from various quarters, and do what I thought was morally right at the time," he wrote.