Leon Goretzka is set for another spell on the sidelines after Bundesliga surprise package Schalke confirmed the midfielder will undergo tests on a leg injury.
Goretzka, a reported target for Bayern Munich, Juventus and Barcelona, has featured twice for Domenico Tedesco's side after recovering from a stress fracture sustained last month.
But the Germany international, who starred in his country's victory at the Confederations Cup, has been ruled out for the forseeable future.
"Leon Goretzka has suffered a recurrence of the injury in his lower leg," Schalke said on Wednesday.
"In order to put these continuous and worsening pains to bed, Leon will undergo examinations over the coming days.
"Until then, it is unclear as to when Leon will be fit to train and play once again. Get well soon, Leon!"
Schalke sit third in the Bundesliga having gone eight games unbeaten under 32-year-old Tedesco, but they are seven points adrift of holders Bayern.
And in-demand Goretzka, whose contract expires at the end of the season, this week suggested he will make a decision over his future in January, with Manchester United reportedly in the race for his signature.
"I have to find out for myself what the next step should be," the 22-year-old said. "I have to consider a million things.
"I am a person who is very meticulous in such decisions. I play through all the scenarios. So I need time.
"There doesn't exist a deadline, but I think we are in the final phase."