The post-US Open period can be the most apathetic on the tennis calendar. The Grand Slam season is closed, winter falls over the major tennis destinations, and monotonous one-dimensional tournaments in indoor arenas take over. It was during this period in 2023 that Jannik Sinner had taken his most significant steps towards becoming a world-beater. He underwent a transformation in mind, body and technique, reaching the final of the year-end ATP Finals and then spurring Italy onto a Davis Cup triumph. It not only pencilled in Sinner’s place among the best in the world, but also marked his best surface: the fast-playing indoor hard courts. ARTICLE CONTINUES BELOW VIDEO Sinner began a winning run on these courts that is yet to be broken, going into 31 consecutive matches and almost two years, after he defeated arch-rival Carlos Alcaraz 7-6(4), 7-5 to win a second successive ATP Finals title on Sunday. He became only the ninth male player to win consecutive year-end Finals title, and the only one to do so without dropping a set. It …