Athletic Bilbao defender Yeray Alvarez, who underwent surgery in December after being diagnosed with testicular cancer, needs chemotherapy.
An abnormality was discovered on Monday during a routine test to monitor the centre-back's recovery from his operation, and the 22-year-old will now need to start a new course of treatment.
The news means Yeray has withdrawn from the Spain squad to play in this month's European Under-21 Championship in Poland, and he is also expected to miss the start of the new LaLiga season.
An Athletic statement read: "An abnormality (adenopathy) has been detected that must be treated, as such in the coming days the player will start an extra treatment (chemotherapy) recommended by the specialists.
"The player will leave today, June 13, the Spain Under-21 squad. The estimated period he will be out for is approximately three months.
"As at the time of his illness, Athletic Club is at Yeray Alvarez's disposal and requests respect and discretion for the privacy of the player and his relatives."
Yeray was diagnosed with a tumour on his right testicle just before Christmas and had the organ removed on December 27.
He made his playing return in the 3-0 defeat to Barcelona on February 4, lasting the full 90 minutes at the Nou Camp, and five days later signed a new long-term contract with Athletic.
Source: PA
