Yeray Alvarez was diagnosed with testicular cancer last year. JEAN-SEBASTIEN EVRARD/AFP/Getty Images

Athletic Bilbao defender Yeray Alvarez has left Spain's under-21 squad after a medical check-up revealed that his testicular cancer has returned, his club announced on Tuesday.

Yeray, 22, will undergo chemotherapy in the coming days and is expected to be out of action for three months. He had been due to take part in the upcoming European Under-21 Championship with Spain.

An Athletic statement said of Alvarez's medical report: "During a radiological check-up done on June 12, the latest of the follow-up tests done to monitor the progress of the testicular tumour that was detected and removed on December 2016, an anomaly [adenopathy] has been detected that needs to be treated and hence, in the coming days the player will undergo complementary treatment [chemotherapy] indicated by the specialists.

"The player will on June 13 leave the U21 Spain national team and the estimated time of absence is approximately three months. Just as we expressed when we first found out about his illness, Athletic Bilbao is at the disposal of Yeray and requests respect and discretion for the player and his family."

Yeray was diagnosed with testicular cancer last year and the defender began playing again in February, less than two months after having a tumour removed.

Yeray posted a message on his Instagram account on Tuesday that read: "When you think you have toppled it, it gets up and it comes back to hit you, but don't worry I'm going to win this battle with the support of all the people and if I have to topple it again, I will do so and I will get up 1,000 times more."

Cuando parece que lo as tumbado se levanta y te vuelve a golpear pero tranquilos que está pelea la voy a ganar con toda esa gente que me apoya y si tengo que volver a tumbarlo lo volveré hacer y me levantare mil y una veces ���������������� A post shared by Yeray (@yerayalvarez) on Jun 13, 2017 at 1:30am PDT

Yeray made his senior debut with Athletic last September and went on to start 25 times in La Liga last season while also making eight Europa League appearances.

Yeray's performances earned him a place in Spain's squad for the European Under-21 Championship.

A youth product of Athletic, Yeray signed a three-year contract extension with the Bilbao-based club in February.