He made his Sarries debut in an Anglo-Welsh clash with Cardiff on 16 January 1999, kicking 11 points in a 36–22 victory.
[3] He made his Premiership debut against Northampton Saints on 6 February 1999 and went on to make 28 appearances for the club in the competition, scoring six tries.
[8] He helped the club secure promotion from National Division One back into the Premiership before returning to Cornwall and Penzance & Newlyn for the 2003–2004 season.
After two seasons with Penzance & Newlyn, Thirlby returned to the Premiership by signing a two-year contract with Gloucester Rugby.
[9] After just ten Premiership appearances and a solitary try, Thirlby joined Redruth on loan in January 2007, agreeing a two-year contract with the club in March 2007.