Having come through the Scarlets Academy system, Sebastian was capped by Wales at U18s level and has played for Carmarthen Quins in the Welsh Premiership.
Sebastian made his Scarlets bow in an LV=Cup match against Cardiff Blues in 2013. He had to wait until 2019 to make his PRO14 debut against Cheetahs.
In January 2021, he signed a new contract to remain at Scarlets.
(LS January 26, 2020)
|2014 - present|
|2015 - 2016|