The 26-year-old forward has not missed a league game in over five years dating back to April 17, 2016, when he was absent for a match against Malaga due to a thigh problem.
Since then, Williams has played in every LaLiga game for his club in each of the last four seasons - and looks set to extend this record to five seasons, with four matches to go in the 2020-21 campaign.
The Spaniard capped off his 191st appearance with an exquisite 90th minute winner into the top corner in what was a huge blow to Sevilla's title chances.
Williams made his first-team debut for Athletic - of which he has been part of the club since 2012 - in December 2014.
Since then, he has scored 65 goals in 292 games for the first-team and was rewarded with a staggering nine-year contract in August 2019, with a release clause set at £117m.