Kelly is one of 10 players picked so far for the Junior Tall Blacks, having played for the Emerging Junior Tall Blacks last September in a three-test series against Australia. Otumoetai College's Derone Raukawa is one of four players vying for one of the final two spots in the team heading for the German city of Mannheim.
Kelly, the son of former breakfast radio host Brian Kelly, first picked up a ball at nine while at St Mary's Primary. Making the tournament team as Tauranga won the under-13 nationals in Dunedin a few years later cemented basketball as his sport.
Kelly said the invite-only Albert Schweitzer tournament, won last year by Australia, would be a tall order for the international minnows, especially after the baptism of fire the national under-17 captain got last year across the Tasman.
The Junior Tall Blacks play Australia at the end of the year in a three-game series in Porirua, with the winner grabbing the Oceania spot at the world champs.
Kelly averaged 12 points and nine rebounds across the three games last September, but said it wasn't until the second game that he truly felt like he belonged.
"Aussie were pretty amazing and gave us a smashing and that first game was a wake-up call, four points and four rebounds, which ruined my stats. Game two was the best I'd played in a while [19 points and 11 rebounds] but we were still well beaten."
Kelly sees himself as an all-round power forward who plays hard on defence but is also a recognised threat on the offensive boards.
His mum said it was a tough decision to leave Aquinas after Year 9 and head to Auckland Grammar to board.
"We were finding we were spending more and more time up there anyway taking Mark up for trainings in a regular basis, which meant less and less time school here," she said.
"Aquinas was great but the compromise was that Mark enrolled as a boarder in Auckland and comes back and stays in Tauranga."