Not that that was his dream, he prefers to be a horse trainer, which is what he is today. "I do not want to take up everything for myself. You have to give other people a chance. I can be a good trainer but a very bad jockey!" he says with a laugh. "So it is better to take off the pressure from me and put it on someone else to deliver."
Being a horse trainer in itself is a lot of work. Our conversation over, thankfully, hot chocolate and dawa is punctuated by calls from people asking him this and that about the horses' upkeep.
Watching clips on the internet of Silverstone Air, one of the greatest horses to ever touch Kenyan soil, takes one's breath away. He is a magnificent beast, dominating the racetrack in a way not many have done. Silverstone was trained by Karari.
He is one of Kenya's best horse trainers, probably the most decorated since 2010. What, exactly, is a trainer?
"First, as a trainer, you have to have horses. Then you have to have workers, and feed manufacturers, apply for your license with the board at the Jockey Club of Kenya to be declared fit to be a horse trainer as they are the stewards of racing.
"Once you get that, you manage the horses, which races they are going to take part in. It takes the eye of a trainer to figure out - is this horse a sprinter, a stayer, a mid-distance, or can it do all of that?" he says.
As a child, Karari would sneak into Ngong Racecourse with the workers, and once there, his eyes would be transfixed on what they were doing. All day.
He never got bored, and his fascination with them only grew as he grew older.
Having grown up next to the racecourse, his aunt would take him to watch the races, fanning the flame inside him. Back then in the nineties, horse racing would draw crowds of upwards of 10,000 people to the racecourse.
"Back then, African jockeys were very few. So when we had our local jockey racing from our local village we would all come and gather to watch. It did not even matter whether he won or lost, just that he was participating. That information would go round the village, that so-and-so was racing. I wanted to be like that. I wanted to be part of it," he says.
He remembers his first time on a horse. The horse's name was Tokyo Joe and it belonged to Ken Coogan, an Irish horse trainer/jockey who was a star in the horse-racing community in Kenya. "He is a very famous icon and had won many classics. We have five classics in Kenya and he had won many of them back to back," says Karari.
"I was maybe 14 or 15. I asked the people at Coogan's stable if I could sit on the horse, so they put me on, bareback. I was so scared that first time. I told them, 'Put me down! Put me down! Put me down!' They said, 'No, nothing is going to happen.' So I sat, and they walked with the horse... And from that time, I have never looked back."
His love for horses had been solidified, but watching veterinarians at work at the stables made him want to do that instead of jockeying.
"I had a chance to hang out with vets who were on the ground treating, stitching the wounds, figuring out what the problem with the horse was, but due to my financial situation, I did not pursue what I wanted. But God has his plans," he says.
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He was still in high school when he went to another stable owned by Oliver Gray, who he refers to as a godfather of the industry.
"So many people have gone through his stable, and he has changed so many people's lives in this country, some of whom are working in places such as Denmark and Dubai. He still trains. It is through his stable that he nurtured local Africans to be who they are today," he says.
Karari asked if he could train there, and by the time he was 18, Gray was confident that he could execute any instructions regarding horses. He would spend all his school holidays at the stables, and when he finished his last paper in high school, the next day he was employed at the stables. That was his university.
I comment that he was very committed, to which he says, "I had that touch of horses. I wanted it and I thought it was fun. I would ask the workers to let me take their horses to the parade ring during races. It was in me. I wanted to take the horse, representing my stable, just so that I could know I did that."
He started as a syce, also known as a groom, who takes care of horses. That was in 2000. He was later promoted to the second head lad, which he explains is like a supervisor. Becoming a horse trainer is an expensive venture, requiring horses, space for the horses, workers and a lot more that goes into keeping horses and training them for racing, so he never imagined he could become one.
"In 2007 I met people who changed my life," he says. They needed someone to work with their horses in Mombasa, but the person he recommended bolted after a day of work. They then insisted that they wanted him specifically for the job, even offering him double the pay he was getting, but he was loath to just leave Gray's stables, given that he was the one who had given him a solid start in his career.
They were willing to wait, however, and eventually, he worked for them.
"I worked there in Mombasa for about a year. They had challenges with their horses and luckily I was able to fix the problems. So my bosses were very happy with my work. They asked me, 'Do you think you can train?' And I said, 'That is what I have been doing here. I have been training your horses. What I learned from the other side is what I applied here,'" he says.
So they opened a stable in Nairobi. They would be the financiers while Karari would manage the stables. To be granted a horse trainer's license in Kenya, you have to be attached to another trainer first for a year. So he interned with Simon Wachira, and within that year he had already trained a winner. Due to some politics, however, it took him two and a half years to get his license.
Karari explains that horse auctions are like football clubs selecting players. At his very first auction, there were 70 of them, and of the horses that later raced from that auction, the one that he had chosen won the races. He kept training winners during the over two years he waited for his license. At one of the auctions, he chose three horses, one of which was the most expensive horse ever auctioned then, the first one in Kenya to be auctioned for Sh2.5 million, back in 2011.
"After being granted my license, it felt like a Jubilee to me. My name would come up in the newspapers as a trainer. The local people here love racing because this is what they know based on where their geographical location has put them, so they were excited to have one of their own as a trainer," he says.
"They gave me support. They were proud when my horses won. It did not matter whether they had bet on it or not. It was one of their own. 'It is our horse'. 'Our horse has won.' It was like my stable became their stable."
That, and having won regular races, gave him the motivation to carry on. Winning the classics was the next step. There are five classics in a year in Kenya: The Kenya Guineas, The Fillies Guineas, The Kenya Derby, the Kenya Oaks and The Kenya St Leger.
He says that winning classics takes luck, a lot of dedication, and knowing the horses very well. He knows trainers who have trained since the 80s and have never won classics. He ended up winning several of them.
The initial horse owners, happy with that, having conquered and having seen enough, hang up their boots and left horse racing. By then, there was a lot of interest from other horse owners for Karari to train them. He opened his stables and at one time was training over 60 horses.
He would eventually buy a horse called Happy Times that would win several classics back to back, then Silverstone Air, a darling of the horse-racing community. He had never won the Kenya Guineas until Silverstone came into the scene, which he finally did in February 2019.
"I have never seen a crowd roar like it did that day. That was when I knew the horse was not mine and did not belong to the owners. It belonged to the fans. The fans jumped into the parade ring. They were holding that horse. We had no space. We could not control the crowd because of how happy they were," he says.
Silverstone, incredibly, also won the triple crown that year, with local jockey James Muhindi. You have to win all the classics in a year to win the triple crown.
Today, Silverstone is retired and a stallion. "He is making babies," says Karari with a smile. He has opened a horse-riding school now.
"I do not see myself quitting horse training, because this is what I love and it does not require someone to retire. My plan is to keep training horses and training human beings how to ride."