Stéfanos Tsitsipás defeated Shintaro Mochizuki 6–3, 6–4 in a United Cup round-robin match on hard court on 2 January 2026. The Greek third seed controlled proceedings with consistent baseline play, breaking serve twice in each set to secure a commanding victory. Mochizuki, competing in the team event, offered resistance in patches but lacked the consistency required to trouble Tsitsipás, who moved through the gears as the match progressed. The two-set win underscored Tsitsipás's early-season form and positioning within his United Cup group.