Last Updated: 11/11/18 6:29pm
Kei Nishikori will feature at the ATP Finals for the fourth time in his career despite not having won a tour-level title in 2018.
The Japanese star began his year by playing on the Challenger Tour where he won a title in Dallas.
Defeats in the finals at Monte-Carlo, Tokyo and Vienna have followed but Nishikori benefited from Juan Martin del Potro's late withdrawal to earn his spot in London.
Having missed the Australian Open to recover from a wrist injury, Nishikori has enjoyed improved performances at each of the remainder of the Grand Slams culminating with a run to the US Open semi-finals.
The 28-year-old started the year outside the world's top 20 but moved back inside the world's top 10 in early November and will aim to improve on two semi-final runs at London's O2.