In a Facebook post, Antetokounmpo said he failed to complete physicals because of excessive pain. Antetokounmpo is in China to attend, but not play in, a basketball tournament in Shanghai.
He was to have rejoined Greece after his China tour, but knee problems alarmed the Bucks, who administered the physical in China.
“It is by far the biggest disappointment in my career,” Antetokounmpo posted in Greek. “I must deal with the problem. Last year, I could `freeze’ the deal on my new extension contract. This year, I have no choice.”
Antetokounmpo’s new four-year, $100 million contract kicks in in September.
He finished in the top-20 in total points, rebounds, assists, steals and blocks last season.