Thiem is the one contender that has made the most consistent progress towards breaking the dominance of the big three.
His excellent movement and effectiveness in both attack and defence have made him a long-time challenger of Djokovic and Nadal in particular.
Quietly confident in his own ability, and calm in the heat of battle. It is a rarity for him to lose his nerve or his temper.
He broke a four-year stranglehold of the Grand Slam titles by Federer, Nadal or Djokovic when he lifted the 2020 US Open title.