Stoke says defender Robert Huth has been diagnosed with the mildest form of viral meningitis following further tests in hospital.
The Premier League team said on its website that the news is "encouraging," adding that "it is too early to predict the length of Huth's absence" but it will be "at least two weeks before he is available to return to action."
The 27-year-old was sent to hospital on Monday after beginning to show meningitis symptoms during Stoke's 11-day tour of the United States.
He will remain in the hospital until he has completed a course of antibiotics.
Huth, who has played 19 internationals for Germany, is likely to miss Stoke's Premier League opener at Reading on August 18.
English Premier League
English Premier League champion Manchester United will start the 2013-2014 season at League Cup winner Swansea.