<Tr> <Td> 2015 </Td> <Td> SRB </Td> <Td> Djokovic, Novak Novak Djokovic </Td> <Td> SUI </Td> <Td> Federer, Roger Roger Federer </Td> <Td> 6--4, 5--7, 6--4, 6--4 </Td> </Tr> <Tr> <Td> 2016 </Td> <Td> SUI </Td> <Td> Wawrinka, Stan Stan Wawrinka </Td> <Td> SRB </Td> <Td> Djokovic, Novak Novak Djokovic </Td> <Td> 6--7, 6--4, 7--5, 6--3 </Td> </Tr> <Tr> <Td> 2017 </Td> <Td> ESP </Td> <Td> Nadal, Rafael Rafael Nadal </Td> <Td> RSA </Td> <Td> Anderson, Kevin Kevin Anderson </Td> <Td> 6--3, 6--3, 6--4 </Td> </Tr> <Table> <Tr> <Td> Event only for USNLTA club members only * </Td> </Tr> <Tr> <Td> Title defended in the challenge round </Td> </Tr> </Table>

Who is the current us open tennis champion
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