5. Marin Cilic
The Croatian had missed the American summer because of injury but he has shown great consistency from the middle of the season onwards, reaching the quarterfinals in 10 out of 12 events.
It's difficult to say how Cilic will fare in 2018 but it's safe to assume that he does have the potential to attain a career-best ranking in the near future.
Prediction: Top 10
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Edited by Musab Abid