"They weren't in Chicago, that's why the IOC (International Olympic Committee) tried to test them in the village," Diack, the head of the International Association of Athletics Federation, said.
The pair have been suspended from the Games by the Greek Olympic Committee pending an IOC hearing on Monday.
Speaking at a news conference after a one-day meeting of the world governing body's ruling council, Diack said the testers had tried to locate Olympic 100 metres champion Kenteris and women's 100 silver medallist Thanou in Chicago on August 10 and 11.
IAAF spokesman Nick Davies said Thanou had been scheduled to remain in Chicago until August 18 while Kenteris was expected to remain until the 23rd.
After failing to locate the pair, the testers, working on behalf of the IOC, which conducts all doping tests between July 31 and August 31, tried again unsuccessfully on August 12 to conduct a test in the Olympic Village.
Kenteris and Thanou, who were kept in hospital overnight last Thursday after a motorcycle crash, will not attend Monday's hearing for medical reasons.
| |||||||||||
"It's a problem that has to be solved but it's a problem that has to be solved by the IOC," he said. "We don't want any athlete taking part in the Olympic Games if there's a doping problem."
Asked later by reporters if he thought the Greeks would compete when the athletics programme opens on Friday he replied: "I don't think so, I don't think so."
Diack said both athletes had been tested twice in the past three months but had missed a test scheduled for Tel Aviv on July 28.
Davies said under World Anti-Doping Agency rules which apply from March 1, athletes face a one-year suspension if they miss three tests in a calendar year.
He said whether or not the two Greeks compete in Athens they could still be banned if the IAAF decides that the Tel Aviv, Chicago and Athens no-shows were missed tests. The council meets again on August 26.
