Sinclair heard the odd abusive remark from adults on the sidelines but, thankfully, selective hearing kicked in.
Helpful hints came from Hawke's Bay referee education officer, Keith Groube, who advised him to set his goals and do his best.
"I was told if people are abusive just ignore them because I'm the person with the whistle," says Sinclair who has lofty aspirations to one day control national provincial championship or Super Rugby level footy.
"It doesn't matter how old you are, you can do anything."
The night before his first match, the former social rugby and basketball player tried to keep his jangled nerves in check.
"I was really nervous so I went to bed trying to remember all these rules.
"The next day I got a couple of things right but a lot of things just went out of the window," he says although he took immense satisfaction from his following games on the platform of incremental improvements, especially with refereeing assessors' constructive criticism.
Running the lines as a touch judge for the reserve grades in the afternoon is also vital in building his confidence.
A part-time worker, who helped out at the family farm of former wife Alison in Putaruru, Waikato, Sinclair hopes to make their 2-year-old daughter, Rylee, proud.
"She [Rylee] is fairly tall for her age already so, hopefully, she'll go on to play for the Silver Ferns."
A lock in his heyday, Sinclair stopped playing because of the demands of finding employment and a niggly knee injury.
Pounding the pavement for an hour a day ensures he attains a certain level of all-round fitness and maintains it.
"I thank God for helping me."
The child of a Croat immigrant, Tanya, and Kiwi father Brian, Sinclair emphasises he has a Maori first name but he hasn't got any Maori blood in him.
"My mother couldn't speak much English so she really struggled to bring me up," he says, adding he doesn't have much to do with his father.
He inherited some of his mother's shortcomings, struggling to assimilate at his boarding high school in Christchurch and eventually grappling with matters pertaining to securing employment.
Groube has allocated Sinclair some junior games so he can "take some baby steps".
"For a big guy, he's nervous and overly confident going in to make calls," he says, adding not everyone can jump into officiating with consummate ease but it always comes down to aspirants getting out what they put in.
Primarily the province struggles in the numbers game with 70 registered refs, but Groube feels the clubs and secondary schools are "quite privileged" even though not all the officials are available every Saturday.
"If you look around the country, not many provincial unions have referees down to the F grades in secondary schools. They tend to have clubs and just down to the first or second 15 in high schools," he says, adding the Madison Trophy in the second half of the season makes life easier considering the reserves play just before the premier teams.
Having played rugby for 40 odd years, the Napier Technical Old Boys past president and life member says the situation will ease a lot if clubs here start taking ownership by offering retired, enthusiastic players the opportunity to carry on in the game. In fact, Groube, who has been refereeing for six years, regrets not returning much earlier as an official from his playing days.
"I was new and I learned a lot from experienced referees throughout the country," he says, emphasising astuteness, a modicum of serenity and possessing more than average management skills are vital prerequisites for the task.
"You have to be a high quality manager with 30 players on the field. You have to be confident and come off a game happy so that's all that matters."
