India, Sept. 9 -- On one of the longest-ever days at the US Open, with all four quarter-final matches going the distance, Ben Shelton vs Carlos Alcaraz had the makings of the match of the tournament, perhaps even the match of the year. The intrigue began from the moment this quarter-final was confirmed on Sunday.

One of the most significant numbers behind Alcaraz's US Open run last year was his serve, which he had revamped at the start of the season, unintentionally replicating Novak Djokovic's motion. This time, perhaps because of the wrist injury that kept him out for more than four months earlier this season, his serve numbers had dipped. The speed had dropped, too.

A leaner Alcaraz had therefore leaned more heavily on another weapon...