Speaking to The Guardian before flying out for the northern hemisphere racing season, said he came away with mixed emotions about his fourth place at Challenge Batemans Bay on Sunday.

In what was his last major race before basing himself in Spain for the next seven months,  Kastelein said his bike leg let him down badly. 

“If you would have asked me a few months ago if I was happy with fourth I would have said ‘yes’,” Kastelein said.  

“But I had higher expectations going into the race and I’m a bit disappointed and frustrated.

“I lost a lot of time on the bike and that was pretty much the difference between winning and fighting for minor places.

“The swim I was in a good position at the end of that, being third out of the water, and I had the fastest run of the day by a fair bit especially over the quality guys.

“It was just the bike leg that let me down.”

Exiting the water after 25.31mins,  Kastelein was 15 minutes slower than eventual winner Sam Appleton on the bike before blazing his way through the last transition and the run leg in 1 hour 15.21 minutes.

While he was around four minutes faster than the winner of the pro category on the run, Appleton was the only competitor to break the four hour-mark with  Kastelein finishing in 4hrs 8mins 12secs. 

“Speaking to him (Appleton) and he said the difference is the strength on the bike comes from years and a big build up and a lot of work behind it, it doesn’t just come if you are new to the sport,”  Kastelein said. 

“So it’s race conditioning and two or three years in the sport in long course events 

“Especially when you start to race the bigger races, the distances make all of the difference especially on the bike. 

“I thought I was in pretty good form on the bike, and Batemans Bay wasn’t a massive race, but it was important to me.”

Kastelein will now take aim at the world titles in Austria in August with several lead-up races hopefully giving him the preparation to start making a name for himself internationally. 

“I’m heading straight to Girona (Spain) with my training partner where we will focus on a couple of half Ironman races and with that I’m hoping to get the financial benefits but also points to qualify for the elites in the half Ironman World Championships,” he said. 

“That’s the ultimate goal for the year. Originally my goal was to get the strength on the bike, get some more race experience on the bike and financially come out on top. 

“But we didn’t expect such good result early on, so we changed our focus and I’ve started to aim a little higher in the World Championships.”

When asked about not being able to fly under the radar now in races inside Australia,  Kastelein said he is glad to have that problem so early in his career. 

“The first couple of races I was a bit of a unknown. Nobody really knew my strengths and my weaknesses so I could hide where I thought I might not be as strong,” he said. 

“The expectations weigh on you a little more, but the other guys plan their races around knowing that I would be one of the faster runners.

“And maybe I am not so strong on the bike. That really showed on the weekend they really pushed the first section of the bike, because they knew they had to get a certain amount of minutes to stay clear of me on the run.”