World ninth Williams won the first set 6-1, but lost the next two 4-6 and 6-7 (5-7).

- Strange conditions, strange situation, but a victory is a victory and I know that everyone is just happy that we can play again, Rogers says after the landslide victory.

It was only the fifth time in her career that Serena Williams lost to an opponent outside the top 100 in the world rankings. The last time was eight years ago when she lost to the then 111-ranked Virginie Razzano in the French Open. 

The WTA tournament was the ninth-ranked Williams' first competitive appearance since February.

The US Open starts on August 31 and then it is important for the 23-time grand slam winner to be in better shape.

CLIP: Serena Williams won against sister Venus

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