Tennis boycott threat and schedule controversy

Top stars Sinner (resting), Djokovic (pacing), and Alcaraz (injured) all skip Montreal Masters; US Open boycott threat escalates. Ben Shelton criticizes schedule demands. Roland Garros proposes prize money increases to stop boycott. Zverev sees opportunity for world No.1 with absent rivals; FAA also a contender. Djokovic's candid admission about physical toll and retirement thoughts adds depth to his fading window for 25th Slam.