The Tennis Integrity Unit (TIU) said that a match alert for a August 30 encounter at the US Open had been received from betting organisations.
Serena Williams is trying to complete the first calendar year Grand Slam since Graf did it in 1988 and match Graf's Open Era record of 22 Grand Slam singles crowns, two shy of Aussie Margaret Court's all-time record.
Serena Williams won 6-0, 2-0 when
Vitalia Diatchenko is not alien to high pressure matches but facing Serena Williams in the opening match of US Open 2015 can still be a very daunting prospect.