Thomas joined us in October 2020 on a long-term contract.
The 27-year-old midfielder had been with Atletico since 2012, making 188 appearances, in which time he won both the Europa League and Super Cup in 2018, and was a Champions League runner-up in 2016.
During his career, Thomas has also enjoyed successful loan spells in Spain with RCD Mallorca (2013/14) and UD Almeria (2014/15), and has made numerous international appearances for Ghana.