Having impressed at the Under-13 Craven Week for Eastern Province in 2006 Isbell was courted by Grey College and went on to represent the Free State at U16 & U18.
In 2010, he was included in an Under-18 High-Performance squad that played in international friendlies against youth sides from France, Namibia and England.
The following year, he was included in the S.A. Schools side that faced a France Invitational side, but missed the game through injury.
He moved to Pretoria in 2012 to join the Blue Bulls Academy. He made ten appearances and scored three tries during the 2012 Under-19 Provincial Championship competition as the Blue Bulls U19 side reached the final of the competition.
At the end of 2012, Isbell received a call-up to the South Africa Sevens side for the 2012–13 IRB Sevens World Series and he made his debut at the 2012 Gold Coast Sevens.
He also played in the Dubai and South African legs of the competition and won a gold medal at the 2013 World Games.
He moved to Nelspruit-based side Pumas in 2014. He was included in their squad for the 2014 Vodacom Cup competition and made his debut for them in the opening match of the season against the Falcons.
He was a member of the Pumas side that won the Vodacom Cup for the first time in 2015, beating Western Province 24–7 in the final. Isbell made three appearances during the season, scoring three tries.
JW July 17
|2014 - present|