Aritz Aduriz announces retirement after doctors recommend hip replacement
The 39-year-old revealed in a social media post that he has made the decision after doctors advised him to have hip replacement surgery.
"The time has become," Aduriz's message began. "Many times, I have said that football will leave you before you leave it.
"Yesterday, the doctors told me to go to see the surgeon, sooner rather than later, to get a prosthetic to replace my hip and to try and go about my everyday life, as normally as possible.
"Unfortunately, my body has said 'enough'. I can't help my team-mates the way I would like to, nor the way that they deserve. That is the life of a professional athlete. Simple, very simple."
Aduriz had intended 2019-20 to be his last season and it seemed he would get the chance of a famous farewell, with Athletic set to face Basque rivals Real Sociedad in the Copa del Rey final.
However, the suspension of the Spanish season due to the coronavirus pandemic means there is no certainty when, or even if, the Copa final will be played.
"Unfortunately, we are living through situations much more grim and painful; the pandemic that we are suffering from has left us with irreparable damage and we have to keep fighting it, together," he said.
"Therefore, I don't want you to worry about me, this is just an anecdote. Let's forget about the finals we dreamt about, because we will have time to say goodbye. And yes, the time has come to say goodbye, and this is how the road ends for me - unforgettable and marvellous, from beginning to end.
"Thank you, from the bottom of my heart."
Aduriz started his senior career with Athletic but also enjoyed spells with Real Valladolid, Real Mallorca and Valencia.
Something of a late bloomer in senior football, he did not join Athletic until he was already 19 and arguably played his finest football in his 30s.
He won his first Spain cap in 2010 before earning a recall six years later at the age of 35, winning a spot in Vicente del Bosque's squad for Euro 2016.
Having decided to end his career after 2019-20, he started the season by scoring a stunning overhead kick to seal a 1-0 win over Barcelona at San Mames last August.
In so doing, he became the only player other than Lionel Messi to score in 15 LaLiga seasons in a row.
However, he only played a further 13 times in LaLiga - all as a substitute - and failed to score again.