He made his Hull Kingston Rovers debut in a Challenge Cup fourth round tie in April 2008,[6] and signed a two-year contract until the end of the 2010 season in June 2008.[7]
After a fine season in 2010 in which Watts played 26 of 27 Super League matches, he was called up to the England training squad for the Four Nations Championship in September 2010,[8] and awarded the 2010 Albert Goldthorpe Rookie of the Year Medal.[9]
Watts requested to be released from his contract with Hull Kingston Rovers in June 2012,[10] and joined Hull F.C. on a three-and-a-half-year contract.[11] Hull coach Peter Gentle said: "Liam is certainly a promising player for the future and we are looking forward to helping him realise his potential".[12] He signed a new three-year contract in July 2014,[13] and a further two-year contract in March 2017.[14]
He spent time on loan from Hull, playing for Doncaster in 2014.
Castleford Tigers
Watts signed for Castleford Tigers on a three-year deal in March 2018.[18] Hull had agreed a fee with Championship side Toronto Wolfpack, but Castleford's "last-minute significant offer" saw him return to Wheldon Road.[19] He made 23 appearances in his first year.
Watts had an outstanding personal season in 2019, playing in all but 2 of Castleford's games and earning a place in the Super League Dream Team.[20] At the club's end of season awards, he was named Player of the Year and Players' Player of the Year, and won the inaugural Immortals Award voted for by Castleford legends.[21] He was also named as the Castleford Tigers Supporters Club player of the year.[22]
In July 2019, he signed a three-year extension until the end of the 2023 season.[23]
Watts played 20 games for Castleford in the 2023 season as the club finished 11th on the table and narrowly avoided relegation.[25]
In the opening match of the 2024 season, Watts was controversially sent off for a high tackle on Wigan's Tyler Dupree,[26][27] under new laws introduced to Super League.[28][29]