"I've done it for the right reason because my family comes first and foremost," explains the Hot Shots Napier Old Boys' Marist cricketer.
While there was an air of inevitability about his retirement, it still came with the same subtlety as his domestic debut - January 17, 1996, when Stu Roberts uprooted his stumps with a first-ball pearler at Lancaster Park, Christchurch.
Sinclair sees his decision now as an opportune time to break cleanly from playing the sport to signal to prospective employers his willingness to embrace myriad challenges in the long term rather than just a six-month stint, in a bid to find traction with his young family.
"It's the best opportunity to market myself in a career that will be sustainable."
With 33 tests, 54 one-day and two Twenty20 internationals under his belt, Sinclair turns his gaze towards the horizon in search of a job after what he describes as "a great ride" in the country's No1 summer sport.
"I don't have any degrees but I do have a degree in life skills," says the man who spent his Octobers to Aprils for the past 19 years in mud-stained whites for first-class campaigns and military green for the shorter forms of the game.
"I'm a great believer in that I have very good transferable skills from cricket to any other environment out there.
"I've enjoyed talking to the media and I suspect they have enjoyed me, too," he says, not long after an interview at his home in Napier with TV3's John Campbell.
Sinclair always set out to make a difference in people's lives, to inspire and motivate them.
His selflessness extends to giving something back to his NOBM club and Hawke's Bay Cricket.
He makes a mental note of putting his feelers out for the 2015 World Cup as a potential commentator with his wealth of experience. "Who knows, I could get back into cricket in sports management or coaching."
For now the Sinclairs will remain in Napier unless a job beckons elsewhere.
While CD have had a seasonal monopoly on him to provide not just skills but to assume the mantle of a vice regal-like role in representing the code, he believes the association is in good hands.
Out of his comfort zone now, Sinclair is experiencing a sense of free-falling into a world of realism. "It's scary but quite challenging."
His attitude to life in the sporting arena was not to settle for second best. "If I scored 200 I always thought, hell, why not 300 or even 400."
The prolific batsman, who also slipped on the gloves behind the stumps to keep wickets and didn't shy from rolling his arm if approached, scored 13,717 runs at an average of 48.64 at first-class level.
He racked up 36 centuries, 68 half tons in helping CD etch their name on eight domestic titles.
Having carved up 214 runs on debut against the West Indies in Wellington in 1999, Sinclair followed that up with an unbeaten 204 against Pakistan the next summer.
If there was a record to break in batting and partnerships at domestic level, you could bet your last dollar the Swiss knife of CD was forever at the cusp of eclipsing it.
However, he will be the first to admit he underachieved internationally in an environment he considers volatile.
"I scored most of my hundreds in the first 12 tests," Sinclair says, adding the 150 against South Africa in the losing test in 2000 at Port Elizabeth out of a total of 298 to his career highlights.
"Unfortunately the rot set in and I couldn't find the form. Cricket is a game where coaches are looking for consistency.
"I started doubting myself and that's the worst thing a batsman can do."
His allegiance to his major association is remarkable, almost unheard of these days.
In fact, two seasons into CD he did flirt with crossing the floor to Wellington or Auckland. The frustration of a nomadic existence in CD's fragmented geographic matrix had left him pondering.
"CD don't have a home ground. You know I wanted to play on a ground where I would get to know every blade of grass because that's how you go about batting to get those big scores."
But his undying sense of loyalty just wouldn't allow him to switch. "CD gave me everything so I felt like I owed them something.
"You don't hear about that sort of loyalty now. It's just not talked about and everyone is for themselves, searching for the dollars."
Nevertheless, he doesn't begrudge the Y Generation's attitude towards securing a future. "I've realised now that you're just a number out there to do a job.
"It was different 20 to 30 years ago but the surroundings are so volatile now so it's pretty tough out there."
While some see it as a selfish trait, Sinclair encourages youngsters to switch allegiances to other major associations because New Zealand is effectively a small pond if they are to realise their potential. He points out former CD player Jesse Ryder's move to Otago Volts from Wellington Firebirds to gain re-selection to the Black Caps as a typical example.
England-born Harry Boam, the first schoolboy to represent Wellington, has retired from domestic cricket at 22 to pursue a career but, he feels, can return to claim a Black Cap when he's graduated. "Will Young [from CD] is doing a degree, too, so good on him," he says, not ruling out part-time studies himself to boost his employability.
Sinclair realises he is the accidental poster boy for a cricketer who once embarked on an exciting journey to be the best cricketer he could be but forgot about the "peripheral" issues from the mainstream of life.
"I wanted to be a great player and you tend to forget about what happens if you break down."
That he didn't miss a game through injury in his entire career isn't a miracle but what Sinclair believes comes down to his "make up".
Carrying a smaller stature, he feels he knew when to switch on and off. "It's an intense game and when the adrenalin kicks in that's when things start to happen to the body," says the man who was wicketkeeper an entire summer for CD, enabling the selectors to pick an extra batsman or bowler. That season the Stags won a title.
"I used to look around and say to myself, 'Heck, I'm not going to be somebody who's going to have four hip replacements and five knee operations."
He puts his longevity down to repetitive skill drills and a degree of aerobic fitness, without frequenting a gym.
He isn't an advocate of religiously pumping irons to build a stronger physical constitution. "I don't agree with lifting heavy weights. Look at Michael Mason who used to go hunting in the bush and was always out and about a lot.
"Mase knew what worked for him so I guess I was pretty similar," he says of the former CD and Black Caps pace bowler from Manawatu.
His book, in the making for a few years, will now have to have a final chapter added before its much-anticipated release, no doubt, considering Sinclair was renowned for his penchant to shoot from the hips.
With CD planning to host a benefit game for him this summer, rumour has it the New Zealand XI team to play the CD XI may have a couple of elite female players.
Sinclair was an advocate of boosting the women's game, never shy to watch or mingle with the CD Hinds players when their paths crossed with the Stags around the country. "The girls are left out at the best of times," he once said.
For now, the gritty cricketer, who served not only his district but his country, is desperately hanging out for a modicum of reciprocity as he asks for middle and leg in the arena of life well before another retirement beckons.
It seems not making Sinclair an offer will be an ignominy or, putting it in the parlance of the summer code, simply not cricket.