The 34-year-old, who has undergone two right hip surgeries in the past three years, also spoke about the adjustments made to his service technique after Wimbledon.
This isn't the first time he's chastised the British tennis system for failing to prioritise the grassroots development of tennis players.
Inordinately long toilets breaks and medical timeouts at critical moments could soon be a thing of the past.
Having eased past Yannick Maden in the first round, Andy Murray had no answer to Safiullin, who won 6-2 4-6 6-1.
Emma Raducanu took New York by storm, en route to her victory as she became the first qualifier in history to claim a grand slam.
Murray was heard speaking to the chair umpire during the match where he was complaining about the length of time Tsitsipas was off the court.
Coco Gauff survived a scare before going past Magda Linette with a 5-7, 6-3, 6-4 victory at the US Open.
Andy Murray lost in the first round of the US Open 2021 with a five-set loss to Stefanos Tsitsipas.
Murray went down gracefully as one of the hardest and longest matches in the history of Grand Slam tournament.
Day 1 also features second seed Daniil Medvedev and eighth seed Casper Ruud against French veterans Richard Gasquet and Jo-Wilfried Tsonga, respectively.