As play gets underway at the Nitto ATP Finals in London, here's a look at the eight teams making up the field at the last tournament of the year.
1
Lukasz Kubot and Marcelo Melo
Playing together for the first time on a regular basis this year, Melo and Kubot have had dominating stretches on all surfaces in 2017. Their unbeaten streak on grass included their first Grand Slam title together at Wimbledon.