Rob McCusker made his Scarlets debut in a friendly match against Exeter Chiefs in August 2007.

Originally from Wrexham, North Wales, McCusker began by playing for Mold Juniors before joining the Scarlets Academy in 2004, through which he made appearances for Narberth, Llanelli RFC, Burry Port and Llandovery. He scored his first 2 tries for the first team in a Heineken Cup match against London Irish in January 2010.

Between 2006 and 2008 McCusker played for Wales Under 20s and the Wales Sevens team. Following good performances, he was called up to the Wales squad for the 2010 summer tour to New Zealand and made his debut in the warm-up match against South Africa at the Millennium Stadium on 5 June 2010.

McCusker has been named Scarlets captain for season 2012-13.