Dominic Thiem - Grigor Dimitrov

Thiem managed to qualify for the ATP World Tour Finals purely based on his form in the initial six months of 2017 where he won the title at ATP Rio de Janeiro, reached the Finals at Madrid Masters and Barcelona, Semi-Finals at Rome Masters and Roland Garros.

Austrian #1 earned as much as point as he could during the clay swing which has kept him in top 10 throughout the entire season, he even got some big wins against the likes of Nadal and Djokovic in Rome and France. Since French Open, Thiem only made one Quarter-Final appearance and that was at ATP Cincinnati (lost to Ferrer 3-6 3-6).

Dimitrov is another player who started the season really well by winning two titles in first two months (ATP Auckland & ATP Sofia) and he even managed to reach the SFs at Australian Open before losing out to Nadal in an epic encounter, but unlike Thiem, Dimitrov has remained consistent throughout the course of the season. Since August 2017, the Bulgarian has won the title at Cincinnati and finished as the runner-up at ATP Stockholm.

In my opinion Dominic is clay type player and Dima is hard court specialist

Open